thread setting plugs and thread plug...

NAVAIR 17-20MD-141

TECHNICAL MANUAL

INSTRUMENT CALIBRATION PROCEDURE

THREAD SETTING PLUGS AND

THREAD PLUG GAGES

DESTRUCTION NOTICE - FOR UNCLASSIFIED, LIMITED DOCUMENTS, DESTROY BY ANY METHOD THAT WILL PREVENT DISCLOSURE OF CONTENTS OR “RECONSTRUCTION OF THE DOCUMENT.”

PUBLISHED BY DIRECTION OF COMMANDER NAVAL AIR SYSTEMS COMMAND

DISTRIBUTION STATEMENT C. DISTRIBUTION AUTHORIZED TO U.S. GOVERNMENT AGENCIES AND THEIR CONTRACTORS TO PROTECT PUBLICATIONS REQUIRED FOR OFFICIAL USE OR FOR ADMINISTRATIVE OR OPERATIONAL PURPOSES ONLY. OTHER REQUESTS FOR THIS DOCUMENT SHALL BE REFERRED TO MEASUREMENT SCIENCE DIRECTORATE, CORONA DIVISION, NAVAL SURFACE WARFARE CENTER, P.O. BOX 5000, CORONA, CA 92878-5000.

MD

-141

M

D-141

1 DECEMBER 2002

THIS PUBLICATION SUPERSEDES NAVAIR 17-20MD-141 DATED 1 JULY 1996

NAVAIR 17-20MD-141

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LIST OF EFFECTIVE PAGES

The purpose of this list is to identify the pages in this document affected by any technical content changes made since the previous release of the document. NOTE: On a revised page, with the exception of the Title, the A, and the i pages, the technical changes are indicated by a vertical line in the outer margin of the page.

Page

No. **

Revision* Page

No. **

Revision* Page

No. **

Revision* Title 0

A 0

i 0

1 to 23 0

25 to 27 0

29 0

A-1, A-2 0

*Zero in this column indicates an original page.

“R” in this column indicates a revised page. **All pages not listed are blank pages.

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TABLE OF CONTENTS

Section Page

1 Introduction and Description ................................................................................................................... 1 2 Equipment Requirements......................................................................................................................... 2 3 Preliminary Operations ............................................................................................................................ 3 4 Calibration Process .................................................................................................................................. 5 4.1 Thread Plug Gage Tests ....................................................................................................................... 5 Navy Calibration Checklist...................................................................................................................... 25 Appendix A: Representative Test Instruments ....................................................................................... A-1

ILLUSTRATIONS

Figure Page

1 Typical Lead Test Configuration ............................................................................................................. 6 2 Thread Plug Gage Pitch Diameter Test Configuration ............................................................................ 15

TABLES

Table Page

1 Calibration Description............................................................................................................................ 1 2 Equipment Requirements......................................................................................................................... 2

NAVAIR 17-20MD-141

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SECTION 1

INTRODUCTION AND DESCRIPTION

1.1 This procedure describes the calibration of W tolerance thread setting plugs or W and X tolerance thread plug gages conforming to the 60° thread form. Thread plug gages are mainly used for the inspection of internal screw threads, or products containing such threads. Thread-setting plugs are primarily used to check thread ring gages by fit, but can also be calibrated in the same manner as thread plug gages. Plugs and gages conforming to a tapered design or to a thread form other than the American National/Unified 60° thread form are not addressed in this procedure. Thread ring and snap gages are excluded from this procedure. However similarities in checking or testing the various types with the tests described herein are acknowledged. Plugs and gages that can be calibrated using this procedure include, but are not limited to, the models and series listed in Appendix A. The plug or gage being calibrated is referred to herein as the TI (Test Instrument).

1.2 All comments concerning this procedure should be directed to Measurement Science Directorate, Corona Division, Naval Surface Warfare Center, P.O. Box 5000, Corona, CA 92878-5000.

1.3 This procedure includes tests of essential performance parameters only. Any malfunction noticed during calibration, whether specifically tested for or not, should be corrected.

Table 1. Calibration Description

TI Characteristics

Performance Specifications

Test Method

Thread setting plug/thread plug gage

Lead Range: 0.0125 up to 0.2500 in Tolerance: ±0.0001 up to ±0.0004 in

Mounted on centers and measured on a universal measuring machine or on an optical comparator.

Major diameter Range: 0.06 up to 6 in Tolerance: ±0.0003 up to ±0.0009 in

Measured on a universal measuring machine, standard measuring machine or supermicrometer.

Effective major diameter Range: 0.06 up to 6 in Tolerance: ±0.0003 up to ±0.0009 in

Same as above, except using one measuring wire. The maximum difference between the measured values is then compared to the major diameter tolerance.

Pitch diameter Range: 0.05 up to 6 in Tolerance: ±0.0001 up to ±0.0006 in

Measured over three measuring wires on a universal measuring machine, standard measuring machine or supermicrometer. An equation is then applied to convert the measurement over the wires to the actual pitch diameter.

Flank angle Range point: 30 deg of arc Tolerance: ±4 up to ±30 min of arc

Projected on the screen of an optical comparator and then measured with the comparator protractor.

Root clearance Range: 0.0016 up to 0.0312 in Tolerance: 0.0016 up to 0.0625 in min

(sharp V); 0.0016 up to 0.0625 in max (V w/undercut)

Projected on the screen of an optical comparator, adjusted vertically and then measured with the comparator horizontal micrometer.

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SECTION 2

EQUIPMENT REQUIREMENTS

NOTES

Minimum use specifications are the principal parameters required for performance of the calibration, and are included to assist in the selection of alternate equipment, which may be used at the discretion of the using laboratory. Satisfactory performance of alternate items shall be verified prior to use. All applicable equipment must bear evidence of current calibration.

The instruments utilized in this procedure were selected from those known to be available at Navy calibration facilities, and the listing by make or model number carries no implication of preference, recommendation, or approval for use by other agencies. It is recognized that equivalent equipment produced by other manufacturers may be capable of equally satisfactory performance in this procedure.

Table 2. Equipment Requirements

Item Minimum Use Specifications

Calibration Equipment

2.1 Universal measuring machine

Range: 0 up to 3.125 in (lead) 0 up to 6 in (diameter)

Uncertainty: ±25 µ in

Societe Genevoise D’Instruments de Physique SIP305M

NOTE

Either item 2.1, 2.2 or 2.3 can be utilized to measure major/pitch diameter. However only item 2.1 or 2.7 can measure lead.

2.2 Standard measuring machine

Range: Total: 0 to 6 in Micrometer: 0 to 1.0 in Uncertainty: ±25 µ in

Pratt &Whitney U304393, or U50077 or U50078

2.3 Supermicrometer Range: Total: 0 to 6 in Micrometer: 0 to 1.0 in Uncertainty: ±30 µ in

Pratt &Whitney U303439

2.4 Protective coating To protect TI threads and body from rust and corrosion

“DIP-PAK”; “SEAL-PEAL”; or Local supply

2.5 Stoddard solvent To clean the TI, 1 gallon container Local supply

2.6 Arkansas stone For cleaning and polishing a TI Local supply

2.7 Optical comparator Protractor range: 0 to 90° Uncertainty: ±1 min Micrometer range: 0 to 1 in Uncertainty: ±0.0001 in

Jones and Lamson Machine PC14A

2.8 Cylindrical half rolls To provide support during the measurement of TI major and pitch diameters, with a flat section to prevent rolling

P/O Pratt &Whitney U50075 accessory kit; or

Local supply

2.9 Gage blocks Range: 0 to 4 in Uncertainty: ±10 µ in

Webber Gage Div. RS88A1 or SS88A1X

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Item Minimum Use Specifications

Calibration Equipment

2.10 Thread measuring wire set Range: TPI: 4 to 80 Diameter: 0.00722 to 0.14434 in Uncertainty: ±20 µ in

Van Keuren 34HS

2.11 Gages and gaging for unified inch screw threads

Reference data ANSI/ASME B 1.2-1983 dated 1983*

2.12 Screw-thread standards for Federal services

Reference data FED-STD-H28A dated 10 September 2001*

* It is the user’s responsibility to ensure conformance with the latest issue of documents referenced above.

SECTION 3

PRELIMINARY OPERATIONS

3.1 If applicable, remove the protective coating (item 2.4) from the TI. Wash the TI with stoddard solvent (item 2.5). Blow the TI dry with clean, dry air, as required.

3.2 Ensure that the TI is clean and free from foreign matter, defects or damage which would impair its serviceability.

3.3 Examine the TI thread flanks for evidence of rust or corrosion, nicks or burrs. Remove rust and/or burrs by applying an arkansas stone (item 2.6). Reject the TI if rust or corrosion is too severe or extensive to be removed, and/or if the corrosion or nicks would interfere with proper mating of the TI with internal threads, as applicable, in normal use.

3.4 Place the TI on a work table or surface plate; allow a minimum of two hours for temperature stabilization before proceeding.

3.5 Ensure that the temperature in the calibration area is maintained within ±4°F of the reference temperature, 68°F, with temperature change limited to 2°F/hour. The humidity should be controlled so as not to exceed 45% RH.

NOTE

Calibration area temperatures as high as 76°F can be tolerated if the TI is allowed to stabilize to a temperature within ±2°F of the measurement device and gage blocks used to zero the measurement device.

3.6 Inspect the TI to determine and record the nominal size, threads per inch (TPI), series designation (UN, UNC, UNF, etc.), class (1B, 2B, 3B), type (GO, NOT GO, HI thread plug gage) and the actual tolerances to be used for lead, major diameter, pitch diameter, flank angle and root clearance, based on the applicable tolerances listed for the TI in ANSI/ASME B 1.2-1983 (item 2.11) or FED-STD-H28 (item 2.12) or other document, as specified. Prepare a checklist for the TI, as necessary, following the checklist examples in this procedure.

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NOTES

TI marking/labeling varies with the manufacturer/user activity practice. Consult ANSI/ASME B 1.2-1983, FED-STD-H28 and/or the user activity for additional information, as necessary, to completely identify the TI and applicable tolerances before proceeding.

This procedure addresses 60° form thread plug gages that are not tapered. The basic methods of measuring major and pitch diameter are not applicable to taper pipe thread plug gages (American Standard NPT pipe threads). Refer to NAVAIR 17-20MD-148L for instructions on the calibration of taper pipe thread plug gages.

The general practice is to interpret the above tolerances as absolute values. For example, a major diameter tolerance of 4.3718 to 4.3720 should be interpreted as 4.37180 to 4.37200.

3.7 Connect the universal measuring machine (item 2.1), standard measuring machine (item 2.2) or the supermicrometer (item 2.3), as applicable, and the optical comparator (item 2.7) to an appropriate power source. Set the applicable power switches to on.

NOTE

If using the universal measuring machine (GSIP 305M), set the power switch (312) at the rear of the electronic control unit (ECU) to on. Set the micro-indicator (TTR 20) rear power (1, 0) switch to 1.

3.8 If using the universal measuring machine, perform the following preparations/self check operations:

3.8.1 Set the micro-indicator TESATRONIC unit controls as follows:

E/mm selector (rear) E

MEASURING RANGE selector 6

A polarity selector +

NOTES

In this procedure, gage head B is not used in the measurement of lead, pitch diameter and major diameter. However, the gage head can be left connected to the rear of the TTR 20 unit.

The position of the A polarity selector has no effect on the direction of the display indications on the ECU. However, it is set to +, the conventional direction for null indications.

3.8.2 Ensure that “INI” is displayed on the ECU digital readout.

3.8.3 Move the carriage to the extreme left, using the large handwheel (110), taking care not to hit the end stop with any appreciable force.

3.8.4 Depress the INIT pushbutton. Ensure that an indication of approximately 300.0000 is displayed. Depress the INCH pushbutton to set up ECU indications in inches.

3.9 Select the proper universal measuring machine/standard measuring machine/supermicrometer gaging force for the measurement to be performed. Record the gaging force on the checklist.

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NOTES

The proper measuring force for TI lead measurements is zero pound force (0 lbf).

The proper measuring force for TI major and pitch diameter measurements is:

LBF TPI 2.5* 4 to 20 1.0 21 to 40 0.5 41 to 80

*The measuring force on the universal measuring machine is limited to 28 ozf, or approximately 1.75 lbf. Since the tolerances for TIs of 4 to 20 threads per inch are generally wider, the effect of using 1.75 lbf in lieu of 2.5 lbf is considered negligible.

3.10 Allow up to 15 minutes for the universal measuring machine/standard measuring machine/supermicrometer to stabilize at the ambient temperature.

NOTE

The measuring machine/supermicrometer should be mechanically/electrically zeroed before beginning any TI thread plug major or pitch diameter measurements or whenever the TI indication changes significantly during a particular measurement.

SECTION 4

CALIBRATION PROCESS

NOTE

Unless otherwise specified, verify the results of each test and take corrective action whenever the test requirement is not met, before proceeding.

4.1 THREAD PLUG GAGE TESTS

4.1.1 Lead, Using the Universal Measuring Machine

NOTES

Measurements of TI lead, or pitch, are based on the use of a universal measuring machine or equivalent instrument designed to measure lead. Lead measurements should be performed during the initial calibration/acceptance of the TI or whenever pitch diameter, flank angle or root clearance measurements indicated that the lead may have been affected by wear.

The instructions in this procedure are based on the used of the GSIP 305M Universal Measuring Machine; if another model is utilized, interpret the instructions accordingly. The 305M is limited to lead measurements of TIs no larger than 3.125 inches in size. For a TI larger than 3.125 inches, proceed directly to section 4.1.2.

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4.1.1.1 Ensure that the center supports (450) and (451) are mounted on the front ways of the universal measuring machine.

4.1.1.2 Adjust the position of the center supports as necessary; place the TI on the centers, as shown in Figure 1. The TI must be supported in a horizontal position.

TI

Figure 1. Typical Lead Test Configuration

NOTE

If the TI has a chip groove, position the TI so that the chip groove is on the bottom. If the TI has a trilock design, it may be necessary to check the crest of the TI threads (full form or truncated) with a height gage to ensure a horizontal alignment to within ±0.0001 to ±0.0002 inch.

4.1.1.3 Lock the TI in position, using the locking knob on the right side center support.

4.1.1.4 Using the force adjustment knob (220), set the measuring force to 0 lbf, as shown on the force indicator (221).

4.1.1.5 Select the appropriate feeler (palpeur), as indicated on the chart of the universal measuring machine, applicable to the TI type (60°) and threads per inch (TPI).

4.1.1.6 Mount the feeler onto the holder slide (230), using the feeler locking knob (2302), to securely tighten the feeler.

NOTE

Do not adjust the feeler locking knob (2302) until step 4.1.1.26 is completed or the measurement accuracy may be compromised.

4.1.1.7 If the TI major diameter is 1/2 inch or greater, multiply the nominal value by 25.4.

4.1.1.8 If the TI major diameter is 1/2 inch or greater, set the holder slide (230) to the mm setting determined in step 4.1.1.7. If the major diameter is less than 1/2 inch, set the slide so that the feeler contacts the center of the thread grove.

4.1.1.9 Lock the slide in position with the feeler slide locking knob (2301).

4.1.1.10 Depress the fine setting pushbutton (112) to unlock the large handwheel (110), as necessary.

4.1.1.11 Turn the large handwheel (110) until the feeler is above the center of the first thread groove.

4.1.1.12 Lower the slide assembly by manipulating the lever (232), and turning the rotating knob (231) to the right of the slide.

4.1.1.13 Carefully continue the lowering action until the feeler tip contacts the first TI thread groove.

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NOTES

By convention, the first thread groove is designated as the first full groove next to the entering end of the TI.

The feeler is designed to contact each thread groove normal to the TI thread axis, at approximately the same groove depth. Variations in the point of contact (relative to the pitch diameter line) will not appreciably affect the accuracy of lead measurements in the horizontal direction.

4.1.1.14 Turn the rotating knob (231) approximately 1/16 to 1/8 turn, as required, to fully seat the feeler in the TI thread groove (groove No. 1).

NOTE

Ensure that the TI does not move or rotate during the lead measurements that follow. Any such movement will compromise the accuracy of the measurements.

4.1.1.15 Adjust the large handwheel (110) to obtain an onscale indication on the micro indicator null meter.

4.1.1.16 Depress the fine setting pushbutton (112), locking the large handwheel (110).

4.1.1.17 Turn the fine setting control knob (111) at the right of the handwheel, until the null indicator is zeroed.

4.1.1.18 Depress the ECU RESET button to zero out the digital display.

NOTE

If a printer is available, it can be attached to the rear of the ECU. The printer can then be commanded to print the measurement indications on the display by simply depressing the ECU PRINT pushbutton.

4.1.1.19 Depress the fine setting pushbutton (112) to unlock the large handwheel (110).

4.1.1.20 Raise the slide assembly by manipulating the lever (232), disengaging the feeler from the thread groove.

4.1.1.21 Adjust the large handwheel (110) to position the feeler at a point above the next thread groove (groove No. 2).

4.1.1.22 Lower the slide assembly by manipulating the lever (232); carefully continue the lowering action until the feeler tip contacts the thread groove.


4.1.1.24 Depress the fine setting pushbutton (112), locking the large handwheel.

4.1.1.25 Turn the fine setting control knob (111) until the null indication is zeroed. Note the indication on the ECU display.

4.1.1.26 Perform steps 4.1.1.19 through 4.1.1.25 for each remaining full thread groove on the TI.

4.1.1.27 Compare each indication obtained in steps 4.1.1.25 and 4.1.1.26 to the nominal lead (pitch) value for the TI thread size at the 0° position (multiplied by the number of grooves traversed). Verify that the maximum algebraic difference between the lead deviations is within the tolerance limits on the calibration checklist, or as listed.

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NOTES

Re-measurement of lead values that are out of tolerance by amounts up to ±0.00003 inch is recommended. Such amounts may be a result of measurement error and not a true out of tolerance condition. Continued use of such a TI is acceptable if all the other test results are satisfactory.

For truncated thread-setting plugs, the differences between the lead deviations must not exceed 0.00010 inch for any group of adjoining threads equal to the length of the associated thread ring gage (if any) or the length of nine threads, whichever is less. The adjoining threads can lie in the truncated portion, full form portion, or both portions of the thread setting plug.

4.1.1.28 Depress the fine setting pushbutton (112), unlocking the large handwheel (110).

4.1.1.29 Raise the slide assembly by manipulating the lever (232), disengaging the feeler from the thread groove.

4.1.1.30 Rotate the TI approximately 90 degrees.

4.1.1.31 Adjust the large handwheel (110) to position the feeler at a point above the first thread groove.

4.1.1.32 Perform steps 4.1.1.22 through 4.1.1.25, then depress the ECU RESET button to zero out the digital display at the first thread groove.

4.1.1.33 Perform steps 4.1.1.19 through 4.1.1.25 for each thread groove, as applicable, on the TI at the 90 degree position. Refer to the Note of step 4.1.1.14 on preventing TI movement, and to the first Note of step 4.1.1.27 on remeasurement of the lead.

4.1.1.34 Raise the slide assembly by manipulating the lever (232), disengaging the feeler from the TI thread groove.

4.1.1.35 Release the locking knob, and slide the right side center support to the right, allowing the TI to be removed.

4.1.2 Lead, Using the Optical Comparator

NOTE

The optical comparator (item 2.7) should be employed only if the TI lead tolerance is ±0.0003 inch or greater. The lead, flank angle, and root clearance can all be measured at the same time, as necessary.

4.1.2.1 Position the TI horizontally between the centers on the worktable of the optical comparator. Support the TI as necessary.

4.1.2.2 Adjust the TI as necessary to ensure that the projected major diameter image is parallel with the horizontal reference line on the screen.

NOTE

Select the highest optical comparator magnification that will project the sharpest possible TI thread profile across the screen. A view of four or five threads is sufficient.

4.1.2.3 Set the helix table to the proper helix angle as specified for the TI. Refer to the Notes of step 4.1.6.28 when calculating the helix angle.

4.1.2.4 Elevate/lower the optical comparator table, as necessary, until the horizontal screen line is parallel and close to the major diameter on the projected TI thread profile.

4.1.2.5 Adjust the horizontal micrometer as necessary to position the 0°00’ vertical reference line parallel, and as close as possible (minimum air gap) to the leading flank of the projected TI thread profile.

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NOTE

The leading flank is the flank of the TI thread that is in front when the TI is screwed into a part.

4.1.2.6 Rotate the screen slowly, using the protractor/angle adjusting arm, as necessary, to obtain an exact and parallel alignment between the TI leading flank and the 0°00’ reference line.

4.1.2.7 Note the indication of the horizontal micrometer to the nearest 0.0001 inch. Zero the indication, as applicable.

4.1.2.8 Adjust the position of the horizontal micrometer to bring the 0°00’ vertical reference line parallel and as close as possible to the leading flank of the next TI thread groove. Note the indication of the horizontal micrometer.

4.1.2.9 Perform steps 4.1.2.5 through 4.1.2.8 for each remaining full thread groove on the TI.

4.1.2.10 Compare each indication obtained in steps 4.1.2.8 and 4.1.2.9 to the nominal lead (pitch) value for the TI thread size at the 0° position (multiplied by the number of grooves traversed). Verify that the maximum algebraic difference between the lead deviations is within the tolerance limits listed. Refer to the Notes of step 4.1.1.27.

4.1.2.11 Rotate the TI approximately 90° and perform steps 4.1.2.2 through 4.1.2.10 for the 90° position.

4.1.2.12 If no other measurements are to be performed on the optical comparator, remove the TI from the comparator worktable.

4.1.3 Major Diameter, Using The Universal Measuring Machine

NOTE

If the universal measuring machine is not available, proceed directly to section 4.1.4.

4.1.3.1 Ensure that the preliminary preparations of sections 3.1 through 3.10, as applicable, have been performed.

4.1.3.2 Position the TI upright between the anvils of the universal measuring machine, with the TI supported by a cylindrical half roll (item 2.8) positioned on an elevating table or other flat support structure.

NOTES

A large TI can be measured in a horizontal position when it is more convenient.

If available, a tiltable, universal measuring table (supplied with item 2.1) may be used to support the TI in lieu of the elevating table and half roll. Since the universal measuring table can be tilted by minute amounts, a half roll is not normally required.

4.1.3.3 Position the TI so that the TI sides are aligned with the center of the opposing machine anvils.

4.1.3.4 Adjust the elevating table or universal measuring table, as applicable, so that the anvils will contact the TI bottom (FRONT) threads.

CAUTION

ENSURE THAT THE UNIVERSAL MEASURING MACHINE HAS BEEN SET TO THE PROPER GAGING FORCE FOR THE TI THREADS PER INCH (TPI) OR DAMAGE TO THE TI THREADS MAY RESULT.

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NOTE

One measuring position, FRONT, is required for TIs with thread length of 0.25 to 0.5 inch. Only two measuring positions, FRONT and BACK, are required for TIs with thread length of 0.5 to 0.75 inch.

4.1.3.5 Set the TI aside. Place gage block(s) between the machine anvils. The dimension of the gage block(s) shall be selected to be equal to the nearest nominal inch over/under the dimension of the TI major diameter, although smaller/larger gage blocks can also be utilized.

4.1.3.6 Ensure that the large handwheel (110) is unlocked and ready for use; adjust the handwheel (110) to obtain an onscale indication on the micro indicator null meter.

4.1.3.7 Depress the fine setting pushbutton (112) to lock the large handwheel (110).

4.1.3.8 Turn the fine setting control knob (111) until the null indication is zeroed.

4.1.3.9 Depress the ECU key representing the nominal dimension of the gage block(s); depress the PRESET button to enter the value as a reference dimension on the ECU display.

4.1.3.10 Depress the fine setting pushbutton (112) to unlock the large handwheel (110).

4.1.3.11 Back off the movable anvil with the handwheel (110) to allow the insertion of the TI.


4.1.3.13 Depress the fine setting pushbutton (112) to lock the large handwheel (110).

4.1.3.14 Tap the TI lightly, and adjust the fine setting control knob (111) as necessary to obtain a minimum diameter indication when the null meter is zeroed.

4.1.3.15 Note the indication as the major diameter value FRONT 1.

4.1.3.16 Retract the movable anvil slightly, using the fine setting control knob (111) only.

4.1.3.17 Rotate the TI 90°, taking care not to disturb the basic measurement setup.

4.1.3.18 Use the fine setting control knob (111) to obtain an onscale indication, then to fine adjust for a null indication.




4.1.3.22 If applicable, adjust the elevating table so that the anvils will contact the middle (CENTER) TI threads. Refer to the Note of step 4.1.3.4.

NOTE

Thread-setting plugs have both a full-form and a truncated major diameter section. If possible, at least one set of measurements (0°, 90°) should be made in each section. However, measurements at the junction of the two sections should be avoided. Generally, FRONT and CENTER measurements can be made in the truncated section.

4.1.3.23 Use the fine-setting control knob (111) to obtain an on scale indication, then to fine adjust for a null indication.

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4.1.3.25 Note the indication as the major diameter value CENTER 1.

4.1.3.26 Perform steps 4.1.3.16 through 4.1.3.19. Note the indication as the major diameter value CENTER 2.


4.1.3.28 If applicable, adjust the elevating table so that the anvils will contact the top (BACK) TI threads. Refer to the Note of step 4.1.3.4.

4.1.3.29 Use the fine setting control knob (111) to obtain an on scale indication, then to fine adjust for a null indication.


4.1.3.31 Note the indication as the major diameter value BACK 1.

4.1.3.32 Perform steps 4.1.3.16 through 4.1.3.19. Note the indication as the major diameter value BACK 2.

4.1.3.33 Determine the largest and smallest of the six values noted among the FRONT values (steps 4.1.3.15, 4.1.3.20), the CENTER values (steps 4.1.3.25, 4.1.3.26) and the BACK values (steps 4.1.3.31, 4.1.3.32). If the TI is a thread setting plug, determine the largest and smallest values of the truncated section separately from those of the full form section.

4.1.3.34 Record the two (four for thread setting plugs) TI major diameters (largest and smallest) on the checklist. Verify that each diameter is within the TI tolerance limits, as determined in section 3.6.

NOTE

Re-measurement of diameters that are out of tolerance by amounts up to ±0.00003 inch is recommended. Such amounts may be a result of measurement error and not a true out of tolerance condition. Continued use of such a TI is acceptable if all the other test results are satisfactory.


4.1.3.36 Adjust the elevating table so that the anvils will contact the middle (CENTER) TI threads.

4.1.3.37 Place the appropriate 60° thread measuring wire (item 2.10) between a TI thread groove and the movable anvil.

NOTE

For best results, the wire should be one of a set of three measuring wires with the correct best wire diameter required for the TI threads per inch (TPI).

4.1.3.38 Holding the wire in place, use the fine setting control knob (111) to obtain an on scale indication, then to fine adjust for a null indication.

4.1.3.39 Tap the TI lightly, readjust the position of the wire as necessary, then final adjust the fine setting control knob (111) to obtain a minimum diameter indication when the null meter is zeroed.

4.1.3.40 Rotate the TI slowly, taking care not to disturb the position of the wire. Note the maximum and minimum diameter indications over a rotation of 180°.

4.1.3.41 Determine the difference between the two values noted in step 4.1.3.40; divide the result by 2 and record it on the checklist.

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4.1.3.42 Verify that the final result obtained in step 4.1.3.41 (effective major diameter, or major to pitch diameter run out) does not exceed the TI major diameter tolerance limits.

NOTE

Re-measurement of the effective major diameter is recommended (if the result is out of tolerance by amounts up to ±0.00003 inch) before rejecting a TI. Such amounts may be a result of measurement error and not a true out of tolerance condition.

4.1.4 Major Diameter, Using The Standard Measuring Machine or Supermicrometer

4.1.4.1 Ensure that the preliminary preparations of sections 3.1 through 3.10, as applicable, have been performed.

4.1.4.2 Position the TI upright between the measuring anvils of the standard measuring machine/supermicrometer, and with the TI supported by a cylindrical half roll (item 2.8) on the elevating table.

NOTE

Large TIs may be calibrated in the horizontal position if convenient and if there is sufficient clearance below the measuring machine/supermicrometer anvils.

4.1.4.3 Position the TI so that the TI centerline is aligned with the center of the opposing measuring machine/supermicrometer anvils.

NOTE

Ensure that the TI chip groove or blunt start, if any, is away from the operator and away from any possible contact with the anvils.

4.1.4.4 Adjust the elevating table height so that the anvils will contact the bottom (FRONT) threads of the TI.

CAUTION

ENSURE THAT THE STANDARD MEASURING MACHINE/SUPERMICROMETER HAS BEEN SET TO THE PROPER GAGING FORCE FOR THE TI THREADS PER INCH (TPI) OR DAMAGE TO THE TI THREADS MAY RESULT.

NOTE

One measuring position, FRONT, is required for TIs with thread lengths of 0.25 to 0.5 inch. Only two measuring positions, FRONT and BACK, are required for TIs with thread lengths of 0.5 to 0.75 inch.

4.1.4.5 If using a supermicrometer with a TI equal to or larger than 1 inch in size, set the TI aside. Place gage block(s) between the micrometer anvils, with the total dimension of the block(s) equal to the nearest nominal inch of/under the dimension of the TI major diameter.

NOTE

Zero the supermicrometer to gage block(s) equal to the nearest 0.1 inch of the TI major diameter if the applicable tolerance is less than ±0.0005 inch or if optimum measurement accuracy is desired.

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4.1.4.6 If using a supermicrometer with a TI equal to or larger than 1 inch in size, zero the supermicrometer to the gage block dimension, then set the gage block(s) aside.

4.1.4.7 Adjust the measuring machine/supermicrometer micrometer until the anvils contact the TI outside diameter, and an on scale indication is obtained on the null meter.

4.1.4.8 Tap the TI lightly, and adjust the micrometer to obtain a minimum diameter indication when the null meter is zeroed.


4.1.4.10 Retract the movable anvil slightly, using the micrometer.

4.1.4.11 Rotate the TI 90°, taking care not to disturb the basic measurement setup.

4.1.4.12 Turn the micrometer to obtain a null indication on the meter.




4.1.4.16 If applicable, adjust the elevating table so that the anvils will contact the middle (CENTER) TI threads. Refer to the Note of step 4.1.4.4.

NOTE

Thread setting plugs have both a full form and a truncated major diameter section. If possible, at least one set of measurements (0°, 90°) should be made in each section. However, measurements at the junction of the two sections should be avoided.



4.1.4.19 Note the indication as the major diameter value CENTER 1.

4.1.4.20 Perform steps 4.1.4.10 through 4.1.4.13. Note the indication as the major diameter value CENTER 2.


4.1.4.22 If applicable, adjust the elevating table so that the anvils will contact the top (BACK) TI threads. Refer to the Note of step 4.1.4.4.



4.1.4.25 Note the indication as the major diameter value BACK 1.

4.1.4.26 Perform steps 4.1.4.10 through 4.1.4.13. Note the indication as the major diameter value BACK 2.

4.1.4.27 Determine the largest and smallest of the six values noted among the FRONT values (steps 4.1.4.9, 4.1.4.14), the CENTER values (steps 4.1.4.19, 4.1.4.20) and the BACK values (steps 4.1.4.25, 4.1.4.26). If the TI is a thread setting plug, determine the largest and smallest values of the truncated section separately from those of the full form section.

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4.1.4.28 Record the two (four for thread setting plugs) major diameters (largest and smallest) on the checklist. Verify that each diameter is within the TI tolerance limits, as determined in section 3.6.

NOTE

Re-measurement of diameters that are out of tolerance by amounts up to ±0.00003 inch is recommended. Such amounts may be a result of measurement error and not a true out of tolerance condition. Continued use of such a TI is acceptable if all the other test results are satisfactory.


4.1.4.30 Adjust the elevating table so that the anvils will contact the middle part of the full form thread portion of the TI.

NOTE

For best results, the wire should be one of a set of three measuring wires with the correct best wire diameter required for the TI threads per inch (TPI).

4.1.4.31 Place the appropriate 60° thread measuring wire (item 2.10) between a TI groove and the movable anvil.

4.1.4.32 Holding the wire in place, adjust the standard measuring machine/supermicrometer micrometer to obtain an on scale null meter indication.

4.1.4.33 Tap the TI lightly, readjust the position of the wire as necessary, then final adjust the micrometer to obtain a minimum diameter indication when the null meter is zeroed.

4.1.4.34 Rotate the TI slowly, taking care not to disturb the position of the wire. Note the maximum and minimum diameter indications over a rotation of 180°.

4.1.4.35 Determine the difference between the two values noted in step 4.1.4.34, divide the result by 2 and record it on the checklist.

4.1.4.36 Verify that the final result obtained in step 4.1.4.35 (effective major diameter, or major to pitch diameter run out) does not exceed the TI major diameter tolerance limits.

NOTE

Re-measurement of the effective major diameter is recommended if the result is out of tolerance by amounts up to ±0.00003 inch. Such amounts may be a result of measurement error and not a true out of tolerance condition. Continued use of such a TI is acceptable if all the other test results are satisfactory.

4.1.5 Pitch Diameter, Using The Universal Measuring Machine

4.1.5.1 Select the set of three 60° thread measuring wires with the correct best wire diameter required for the TI threads per inch (TPI).

4.1.5.2 Position the TI upright between the anvils of the universal measuring machine, with the TI supported by a cylindrical half roll positioned on an elevating table or other flat support structure. Refer to the Notes of steps 4.1.3.2 regarding the possible use of a universal measuring table or the calibration of large TIs in the horizontal position.

4.1.5.3 Position the TI so that the TI threads are aligned with the center of the opposing machine anvils.

4.1.5.4 Adjust the elevating table or universal measuring table, as applicable, so that the anvils will contact the measuring wires at the TI bottom (FRONT) threads, as shown in Figure 2.

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4.1.5.5 Hold the two wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across, and position the third wire between the groove and the face of the movable anvil. Secure the TI and the three wires in place by adjusting the fine setting control knob (111).

NOTE

Ensure that the large handwheel (110) is locked in place before making fine adjustments.

MOVABLE MICROMETER

ANVIL

CYLINDRICAL HALF-ROLL

(IF REQUIRED)

THREAD MEASURING

WIRES

ELEVATING TABLE

FIXED ANVIL

BACK

CENTER

FRONT

THREAD MEASURING WIRE

Figure 2. Thread Plug Gage Pitch Diameter Test Configuration

4.1.5.6 Turn the fine setting control knob (111) until the null indicator is zeroed.

4.1.5.7 Tap the TI lightly, readjust the position of the wires as necessary, then final adjust the fine setting control knob (111) to obtain a minimum diameter indication when the null meter is zeroed.

4.1.5.8 Note the indication as the measurement over wires dimension FRONT 1.

4.1.5.9 Carefully and slowly rotate the TI 90°, taking care not to disturb the position of the measuring wires.

4.1.5.10 Tap the TI lightly, readjust the position of the wires as necessary, then final adjust the fine setting control knob (111) to obtain a minimum diameter indication when the null meter is zeroed.


4.1.5.12 Retract the movable anvil slightly, using the fine setting control knob (111) only. Carefully remove the measuring wires.

4.1.5.13 Adjust the elevating table or universal measuring table, as applicable, so that the anvil will contact the TI middle (CENTER) threads.

2.8

2.10

2.10

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4.1.5.14 Place the two wires between the middle two TI thread grooves; hold the wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across, and position the third wire between the groove and the face of the movable anvil.

4.1.5.15 Secure the TI and the three wires in place by adjusting the fine setting control knob (111).

4.1.5.16 Perform steps 4.1.5.6 and 4.1.5.7. Note the indication as the measurement over wires dimension - CENTER 1.

4.1.5.17 Perform steps 4.1.5.9 and 4.1.5.10. Note the indication as the measurement over wires dimension - CENTER 2.

4.1.5.18 Retract the movable anvil slightly, using the fine setting control knob (111) only. Carefully remove the measuring wires.

4.1.5.19 Adjust the elevating table or universal measuring table, as applicable, so that the anvils will contact the TI top (BACK) threads.

4.1.5.20 Place the two wires between the top two TI thread grooves; hold the wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across and position the third wire between the groove and the face of the movable anvil.

4.1.5.21 Secure the TI and the three wires in place by adjusting the fine setting control knob (111).

4.1.5.22 Perform steps 4.1.5.6 and 4.1.5.7. Note the indication as the measurement over wires dimension - BACK 1.

4.1.5.23 Perform steps 4.1.5.9 and 4.1.5.10. Note the indication as the measurement over wires dimension - BACK 2.

4.1.5.24 Determine the largest and smallest of the six values noted among the FRONT values (steps 4.1.5.8, 4.1.5.11), the CENTER values (steps 4.1.5.16, 4.1.5.17) and the BACK values (steps 4.1.5.22, 4.1.5.23).

NOTES

Either a simplified or complex equation can be used to calculate the TI pitch diameter. The simplified formula applies in most instances. However, the complex formula should be selected if the two equations yield results which differ by more than 0.00015 inch or if the TI helix angle is determined to exceed 5° by calculation or based on previous calibration data.

If the helix angle is unknown, first calculate the tangent of the helix angle, using the equation:

dleadtanπ

=λ

where the lead is obtained from the table of item 2.11 or 2.12, as applicable

π = 3.1416, and d = the nominal TI pitch diameter.

With the tangent of the helix angle established to four places, the angle may be obtained from a table of natural tangents or by using the INV-TAN keys of a calculator.

If is also possible to obtain the helix angle of most TIs from the appropriate tables or the helix angle chart in MIL-STD-120.

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4.1.5.25 SIMPLIFIED EQUATION: Calculate the TI pitch diameter using the largest value of step 4.1.5.24, as follows:

E = MW -

−

n86603.0W3

Where E = TI pitch diameter, calculated to the nearest 0.00001 inch

Mw = TI measurement over the wires, measured to the nearest 0.00001 inch

W = average thread measuring wire diameter, as provided on the Report of Calibration, to the nearest 0.00001 inch

n = number of TI threads per inch (TPI)

NOTE

The value

3 W -

0.86603n may be provided as the calibrated constant, C, on the Report of Calibration for the

set of measuring wires in use.

4.1.5.26 COMPLEX EQUATION: Calculate the TI pitch diameter using the largest value of step 4.1.5.24, as follows:

E = MW - ∗

−+

n86603.0

)nd(W076.0W3 2

*The term “d” above is the nominal pitch diameter from the tables, rounded off to the nearest 0.001 inch.

4.1.5.27 Perform the calculations of step 4.1.5.25 or 4.1.5.26, as applicable, but for the smallest value noted in step 4.1.5.24.

4.1.5.28 Record the two calculated TI pitch diameters (larger, step 4.1.5.25 or 4.1.5.26) (smaller, step 4.1.5.27) on the checklist. Verify that the two values are within the TI tolerance limits as determined in section 3.6.

NOTE

Re-measurement of diameters that are out of tolerance by amounts up to ±0.00003 inch is recommended before rejecting a TI. Such amounts may be a result of measurement error and not a true out of tolerance condition.

4.1.5.29 Compare the FRONT (step 4.1.5.8, 4.1.5.11), CENTER (steps 4.1.5.16, 4.1.5.17) and BACK (steps 4.1.5.22, 4.1.5.23) measurement over wires dimensions. Verify that the FRONT dimensions are equal to or greater than the CENTER and BACK dimensions, and that the CENTER dimensions are equal to or greater than the BACK dimensions.

NOTES

The purpose of the above comparison is to verify that the TI has no back taper (TI pitch diameter increasing from front to back). The test applies only to thread setting plugs.

Allowance should be made for measurement error of up to ±0.00005 inch when comparing dimensions. If is not strictly necessary to calculate all six pitch diameters before performing the comparisons.

4.1.5.30 Retract the movable anvil, and remove the TI and the measuring wires from the test setup. Proceed directly to section 4.1.7.

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4.1.6 Pitch Diameter, Using The Standard Measuring Machine Or Supermicrometer

4.1.6.1 Select the set of three 60° thread measuring wires with the correct best wire diameter for the TI threads per inch (TPI).

4.1.6.2 Position the TI upright between the anvils of the standard measuring machine/supermicrometer, with the TI supported by a cylindrical half roll on the elevating table. Refer to the Note of step 4.1.4.2 regarding the calibration of large TIs in the horizontal position.

4.1.6.3 Position the TI so that the TI centerline is aligned with the center of the opposing measuring machine/supermicrometer anvils.

4.1.6.4 Adjust the elevating table height so that the anvils will contact the bottom (FRONT) threads of the TI. See Figure 2 for the typical pitch diameter test configuration.

4.1.6.5 Hold the two wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across, and position the third wire between the groove and the face of the movable anvil. Secure the TI and three wires in place by adjusting the measuring machine/supermicrometer micrometer.

4.1.6.6 Adjust the measuring machine/supermicrometer micrometer to obtain an onscale null meter indication.




4.1.6.10 Tap the TI lightly, readjust the position of the wires as necessary, then final adjust the micrometer to obtain a minimum diameter indication when the null is zeroed.


4.1.6.12 Retract the measuring machine/supermicrometer movable, anvil and carefully remove the measuring wires.

4.1.6.13 Adjust the elevating table so that the anvils will contact the middle (CENTER) TI threads.

4.1.6.14 Place the two wires between the middle two TI thread grooves; hold the wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across, and position the third wire between the groove and the face of the movable anvil. Secure the TI and three wires in place by adjusting the measuring machine/supermicrometer micrometer.

4.1.6.15 Adjust the micrometer to obtain an on-scale null meter indication.


4.1.6.17 Note the indication as the measurement over wires dimension CENTER 1.


4.1.6.19 Tap the TI lightly, readjust the position of the wires as necessary, then final adjust the micrometer to obtain a minimum diameter indication when the null meter is zeroed.

4.1.6.20 Note the indication as the measurement over wires dimension CENTER 2.

4.1.6.21 Retract the measuring machine/supermicrometer movable anvil, and carefully remove the measuring wires.

4.1.6.22 Adjust the elevating tale so that the anvils will contact the top (BACK) TI threads.

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4.1.6.23 Place the two wires between the top two TI thread grooves; hold the wires in place by pressing the TI lightly against the fixed anvil. Starting with the lowest wire, follow the thread groove across, and position the third wire between the groove and the face of the movable anvil. Secure the TI and three wires in place by adjusting the measuring machine/supermicrometer micrometer.

4.1.6.24 Perform steps 4.1.6.15 and 4.1.6.16.

4.1.6.25 Note the indication as the measurement over wires dimension BACK 1.

4.1.6.26 Perform steps 4.1.6.18 and 4.1.6.19.

4.1.6.27 Note the indication as the measurement over wires dimension BACK 2.

4.1.6.28 Determine the largest and smallest of the six values noted among the FRONT values (step 4.1.6.8, 4.1.6.11), the CENTER values (step 4.1.6.17, 4.1.6.20) and the BACK values (steps 4.1.6.25, 4.1.6.27).

NOTES

Either a simplified or complex equation can be used to calculate the TI pitch diameter. The simplified formula applies in most instances. However, the complex formula should be selected if the two equations yield results which differ by more than 0.00015 inch or if the TI helix angle is determined to be excessive by calculation or based on previous calibration data.

If the helix angle is unknown, first calculate the tangent of the helix angle, using the equation:

dleadtanπ

=λ

where the lead is obtained from the table of item 2.11 or 2.12, as applicable π = 3.1416, and d = the nominal TI pitch diameter.

With the tangent of the helix angle established to four places, the angle may be obtained from a table of natural tangents or by using the INV-TAN keys of a calculator.

If is also possible to obtain the helix angle of most TIs from the appropriate tables or the helix angle chart in MIL-STD-120.

4.1.6.29 SIMPLIFIED EQUATION: Calculate the TI pitch diameter using the largest value of step 4.1.6.28, as follows:

E = MW -

3 W -

0.86603n

Where E = TI pitch diameter, calculated to the nearest 0.00001 inch

Mw = TI measurement over the wires, measured to the nearest 0.00001 inch

W = average thread measuring wire diameter, as provided on the Report of Calibration, to the nearest 0.00001 inch

n = number of TI threads per inch (TPI)

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NOTE

The value

3 W -

0.86603n may be provided as the calibrated constant, C, on the Report of Calibration for the

set of measuring wires in use.

4.1.6.30 COMPLEX EQUATION: Calculate the TI pitch diameter using the largest value of step 4.1.6.28, as follows:

E = MW - ∗

−+

n86603.0

)nd(W076.0W3 2

* The term “d” above is the nominal pitch diameter from the tables, rounded off to the nearest 0.001 inch.

4.1.6.31 Perform the calculations of step 4.1.6.29 or 4.1.6.30 as applicable, but for the smallest value noted in step 4.1.6.28.

4.1.6.32 Record the two calculated pitch diameters (larger, step 4.1.6.29 or 4.1.6.30) (smaller, step 4.1.6.31) on the checklist. Verify that the two values are within the TI tolerance limits as determined in section 3.6.

NOTE

Remeasurement of diameters which are out of tolerance by ±0.00003 inch is recommended. Such amounts may be a result of measurement error and not a true out of tolerance condition. Continued use of such a TI is acceptable if all the other test results are satisfactory.

4.1.6.33 Retract the measuring machine/supermicrometer movable anvil, using the micrometer.

4.1.6.34 Remove the TI and measuring wires from the test setup.

NOTES

The purpose of the above comparison is to verify that the TI has no back taper (TI pitch diameter increasing from front to back). The test applies only to thread setting plugs.

Allowance should be made for measurement error of up to ±0.00005 inch when comparing dimensions. If is not strictly necessary to calculate all six pitch diameters before performing the comparisons.

4.1.6.35 Remove the TI and measuring wires from the test setup.

4.1.7 Flank Angle

NOTES

Flank angle measurements should be performed only during the initial calibration/acceptance of the TI, or whenever major/pitch diameter measurements indicate that there may be a problem with the flank angle.

The flank angle is the angle between the flank and the perpendicular to the axis of the TI thread, measured in an axial plane. The flank angle of a symmetrical thread is commonly referred to as the half angle.

The method of measuring flank angle in this paragraph is based on the use of an optical comparator, with or without a worm drive, and without a Jones and Lamson CX-327 Thread Screen. Other methods based on the use of the universal measuring machine with the goniometric microscope or other equipment are not addressed in this procedure.

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4.1.7.1 Position the TI horizontally between the centers on the worktable of the optical comparator (item 2.7), set the comparator screen protractor to 0° 00’. Support the TI as necessary.

4.1.7.2 Adjust the TI as necessary to ensure that the projected major diameter image is parallel with the horizontal reference line on the screen.

NOTE

Select the highest optical comparator magnification that will project the sharpest possible TI thread profile across the screen. A view of four or five threads is sufficient.

4.1.7.3 Set the helix table to the proper helix angle as specified for the TI. Refer to the Notes of step 4.1.6.28 when calculating the helix angle.

4.1.7.4 Elevate/lower the optical comparator table, as necessary, until the horizontal screen line is parallel and close to the major diameter on the projected TI thread profile.

4.1.7.5 Adjust the comparator screen protractor or angle adjusting worm, as applicable, to obtain an indication of 0° 0’ on the screen vernier and scale.

4.1.7.6 Adjust the horizontal micrometer as necessary to position the 0° 00’ vertical reference line parallel and as close as possible (minimum air gap) to the leading flank of the projected TI thread profile.

NOTE

The leading flank is the flank of the TI thread that is in front when the TI is screwed into a part. The trailing flank is the flank behind the leading flank.

4.1.7.7 Rotate the screen slowly, using the protractor/angle adjusting worm, as necessary, to obtain an exact and parallel alignment between the TI leading flank and the 0° 00’ reference line.

4.1.7.8 Record the indication of the screen vernier and scale to the nearest degree and minute. Verify that the indication is within the tolerance limits listed for the TI flank angle.

4.1.7.9 Perform steps 4.1.7.6 through 4.1.7.8, except for the TI trailing flank.

4.1.7.10 Adjust the comparator screen protractor/angle adjusting worm to obtain an indication of 0° 00’ on the screen vernier and scale.

4.1.8 Root Clearance

NOTE

Root clearance measurements should be performed only during the initial calibration/acceptance of the TI, or whenever major/pitch diameter measurements indicate that there may be a problem with the root clearance.

4.1.8.1 Ensure that the section 4.1.7 has been performed, with the TI positioned between centers on the optical comparator worktable.

4.1.8.2 Adjust the screen protractor/angle adjusting worm, and the horizontal/vertical micrometers, as necessary, to align the screen 30° 0’ reference lines (if available) with the projected image of the TI leading and trailing flanks. The horizontal line should cross the theoretical point of the V, if the V is not undercut.

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4.1.8.3 Refer to the following table to determine the amount of vertical adjustment required, in accordance with the applicable TI TPI and design.

ROOT CLEARANCE TPI VERTICAL ADJUSTMENT*

(in.) (in.)** (in.)***

80 0.0014 0.0016 0.0031 72 0.0015 0.0017 0.0035 64 0.0017 0.0020 0.0039 56 0.0019 0.0022 0.0045 48 0.0023 0.0026 0.0052 44 0.0025 0.0028 0.0057 40 0.0027 0.0031 0.0062 36 0.0030 0.0035 0.0069 32 0.0034 0.0039 0.0078 28 0.0039 0.0045 0.0089 27 0.0040 0.0046 0.0093 24 0.0045 0.0052 0.0104 20 0.0054 0.0062 0.0125 18 0.0060 0.0069 0.0139 16 0.0068 0.0078 0.0156 14 0.0077 0.0089 0.0179 13 0.0083 0.0096 0.0192 12 0.0090 0.0104 0.0208 11.5 0.0094 0.0109 0.0217 11 0.0098 0.0114 0.0227 10 0.0108 0.0125 0.0250

9 0.0120 0.0139 0.0278 8 0.0135 0.0156 0.0312 7 0.0155 0.0179 0.0357 6 0.0180 0.0208 0.0417 5 0.0217 0.0250 0.0500 4.5 0.0241 0.0278 0.0556 4 0.0271 0.0312 0.0625

* Taken from Col 7, Table 2.1, FED-STD-H28, Section 2 (1978) and rounded off to the nearest 0.0001 inch. ** Use this column for all thread setting plugs and all TIs with a straight “V”. *** This column applies only to NOT GO (HI) thread plug gages with an undercut “V”.

NOTE

The root clearance values listed in the above table apply basically to TIs constructed in accordance with ANSI/ASME B 1.2-1983 or FED-STD-H28 specifications and tolerances. If a TI is constructed in accordance with a particular Military Specification, Military Standard or Federal Standard, consult the applicable document regarding root clearance values and tolerances.

4.1.8.4 Using the vertical micrometer, lower the optical comparator worktable by the amount of vertical adjustment determined in step 4.1.8.3. Ensure that the horizontal line on the comparator screen is clear of the TI thread roots.

4.1.8.5 Looking at one of the central thread roots, use the horizontal micrometer to measure the dimension traversed from the leading flank to the trailing flank, across the “V” or at the bottom of the “V”, as applicable, to the nearest 0.0001 inch.

4.1.8.6 If the TI root is a straight “V”, verify that the dimension across the “V” equals or exceeds the applicable root clearance listed in the first column (**) of the table, according to the TI TPI.

4.1.8.7 If the TI root “V” is undercut, verify that the dimension across the undercut equals or is less than the root clearance listed in the appropriate column (**), (***) of the table, according to the TI TPI and design. The second column (***) applies only to NOT GO (HI) thread plug gages.

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(24 blank) 23

4.1.8.8 Remove the TI from the centers of the optical comparator worktable.

4.1.8.9 If no other measurements are to be performed, set all applicable power switches to off, and secure the equipment.

4.1.8.10 If a protective coating was removed from the TI in section 3.1, and/or it is required to protect the TI threads, apply a similar coating to the TI, following standard practice.

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25

CALIBRATION CHECKLIST TEST INST(S) Southern Gage Co. 1.25-12UNF-2A GO NOT GO Thread-Setting Plug Set

PROC. NO. NA 17-20MD-141 MFR. MODEL SER. NO.

PROCEDURE MEASURED VALUES OUT

STEP FUNCTION TESTED NOMINAL FIRST RUN SECOND RUN OF CALIBRATION TOLERANCES

NO TOL

(1) (2) (3) (4) (5) (6) (7)

3.2/3.3 TI inspection ck( ) NA

(size) (TPI) (Series)

3.6 TI data 1.250 12 UNF NA

(class) (type) (tol)

” 2A GO W NA

3.9 TI gaging force 2.5 lbf NA

4.1 Thread Plug Gage Tests

4.1.1 Lead, GO plug (in) 0° (in) 90° (in) (in)

4.1.1.25/ Thread groove diff per thread 0.08333 0.00020 max

4.1.1.33 ” any 9 threads ” 0.00010 max

4.1.3/4.1.4 Major Diameter, GO plug (in) (in) (in)

4.1.3.34/ Largest value (truncated) 1.23530 1.23470 to 1.23530

4.1.4.28 Smallest ” ” ” ”

” Largest value (full form) 1.24820 1.24820 to 1.24880

” Smallest ” ” ” ”

4.1.3.42/ Effective major diameter 0.00000 -0.00030 to +0.00030

4.1.4.36 (run out)

4.1.5/4.1.6 Pitch Diameter, GO plug (in) (in) (in)

” Largest value 1.19410 1.19390 to 1.19410

” Smallest value ” ”

4.1.7 Flank Angle (°, min) (°, min) (degrees, minutes)

4.1.7.8 Leading flank 30° 0’ 29° 54’ to 30° 06’ 4.1.7.9 Trailing flank ” ”

4.1.8 Root Clearance (in) (in) (in)

4.1.8.6 Straight V dimension 0.0104 min

Page 1 of 2

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CALIBRATION CHECKLIST TEST INST(S) Southern Gage Co. 1.25-12UNF-2A GO NOT GO Thread-Setting Plug Set




NO TOL

(1) (2) (3) (4) (5) (6) (7)


4.1.1 Lead, NOT GO plug (in) 0° (in) 90° (in) (in)

4.1.1.25 Thread groove diff per thread 0.08333 0.00020 max

4.1.1.33 Thread groove diff any 9 threads ” 0.00010 max

4.1.3/4.1.4 Major Diameter, NOT GO plug (in) (in) (in)

4.1.3.34 Largest value (truncated) 1.22400 1.22340 to 1.22400

4.1.4.28 Smallest ” ” ” ”




4.1.4.36 (run out)

4.1.5/4.1.6 Pitch Diameter, NOT GO plug (in) (in) (in)

” Largest value 1.18790 1.18790 to 1.18810






Page 2 of 2

NAVAIR 17-20MD-141

(28 blank) 27

CALIBRATION CHECKLIST TEST INST(S) Southern Gage Co. 2-56UNC-2A NOT GO Thread-Setting Plug




NO TOL

(1) (2) (3) (4) (5) (6) (7)



3.6 TI data 0.086 56 UNC NA


” 2A NOT GO W NA



4.1.1 Lead (in) 0° (in) 90° (in) (in)


4.1.1.33 ” any 9 threads ”

4.1.3/4.1.4 Major Diameter, GO plug (in) (in) (in)

4.1.3.34/ Largest value (truncated) 0.07940 0.07910 to 0.07940

4.1.4.28 Smallest ” ” ” ”




4.1.4.36 (run out)

4.1.5/4.1.6 Pitch Diameter (in) (in) (in)

” Largest value 0.07170 0.07170 to 0.07180






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NAVAIR 17-20MD-141

29

CALIBRATION CHECKLIST TEST INST(S) National Twist Drill 7/16-20UNF-3B Thread Plug Gage, GO Type




NO TOL

(1) (2) (3) (4) (5) (6) (7)



3.6 TI data 0.4375 20 UNF NA


” 3B GO X NA



4.1.1 Lead, GO Plug (in) 0° (in) 90° (in) (in)


4.1.1.33 ” any 9 threads ”

4.1.3/4.1.4 Major Diameter (in) (in) (in)

4.1.3.34/ Largest value 0.43750 0.43750 to 0.43800

4.1.4.28 Smallest ” ” ”


4.1.4.36 (run out)

4.1.5/4.1.6 Pitch Diameter (in) (in) (in)

” Largest value 0.40500 0.40500 to 0.40530






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NAVAIR 17-20MD-141

A-1

APPENDIX A

REPRESENTATIVE TEST INSTRUMENTS

TIs which may be calibrated using this procedure include, but are not limited to, the following:

MODEL/SERIES MANUFACTURER NOMENCLATURE TOLERANCE

FD 45891 Lockheed Corp Thread Plug Gage X NPSH Widell Industries Thread Plug Gage X UN Green Instrument Co. Thread Plug Gage X ” Regal-Beloit Corp. Thread Plug Gage X ” Southern Gage Co. Thread Plug Gage X ” Widell Industries Thread Plug Gage X UNC Greenfield Div., TRW Thread Plug Gage X ” J &L Industries Thread Plug Gage X ” Johnson Gage Co. Thread Plug Gage X ” Mercury Gage Co. Thread Plug Gage X ” Pennoyer-Dodge Co. Thread-Setting Plug W ” Regal-Beloit Corp. Thread Plug Gage X ” Size Control Co. Thread Plug Gage W,X ” Southern Gage Co. Thread Plug Gage X ” Thredco Co. Thread Plug Gage X UNEF Widell Industries Thread Plug Gage X UNF Acme United Corp. Thread Plug Gage X ” Alameda Gage Co. Thread Plug Gage X ” Greenfield Div., TRW Thread Plug Gage X ” J &L Industries Thread Plug Gage X ” Johnson Gage Co. Thread Plug Gage X ” Mercury Gage Co. Thread Plug Gage X ” National Twist Drill Thread Plug Gage X ” Regal-Beloit Corp. Thread Plug Gage X ” Size Control Co. Div. Thread Plug Gage X ” Southern Gage Co. Thread Plug Gage X ” ” Thread-Setting Plug W ” Swiss Precision Instr. Co. Thread Plug Gage X ” Van Keuren Thread Plug Gage X ” Widell Industries Thread Plug Gage X UNJF Johnson Gage Co. Thread Plug Gage X ” Southern Gage Co. Thread Plug Gage X UNS Johnson Gage Co. Thread Plug Gage X 10-32NF-3A Alameda Gage Co. Thread-Setting Plug W 1-14UNS-3A Southern Gage Co. Thread-Setting Plug W 1-1/8-12UNF-2A ” Thread-Setting Plug W 1-1/8-16UN3A Pennoyer-Dodge Co. Thread-Setting Plug W 1-8UNC-2A GO Southern Gage Co. Thread-Setting Plug W 1-8UNC-2A NOT GO ” Thread-Setting Plug W 1/2-13UNC-2A ” Thread-Setting Plug W 1.25-12UNF-2A ” Thread-Setting Plug W 1/4-20UNC-3A ” Thread-Setting Plug W 1/4-20UNC-3B GO NO GO National Twist Drill Thread Plug Gage X 1/4-28UNF-3B GO NO GO ” Thread Plug Gage X 1.5-12UNF-2B Greenfield Div., TRW Thread Plug Gage X 1.5-6UNC-2A GO NO GO Van Keuren Thread Plug Gage X 2-56UNC-2A Southern Gage Co. Thread-Setting Plug W 3/8-24UNF-2A Southern Gage Co. Thread-Setting Plug W 5/16-18UNC-2A ” Thread-Setting Plug W

NAVAIR 17-20MD-141

A-2

MODEL/SERIES MANUFACTURER NOMENCLATURE TOLERANCE

5/8-11UNC-3B National Twist Drill Thread Plug Gage X 7/16-14UNC-3B ” Thread Plug Gage X 7/16-20UNF-3A Southern Gage Co. Thread-Setting Plug W 7/16-20UNF-3B National Twist Drill Thread Plug Gage X 7/8-9UNC-2A Southern Gage Co. Thread-Setting Plug W 9/16-12UNC-2A ” Thread-Setting Plug W 9/16-18UNF-2A ” Thread-Setting Plug W

thread setting plugs and thread plug...

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