identifying threads

Identifying Threads

Using the thread identification kit from Malone Specialty Inc. or a commercially available

caliper, thread gauge and thread pitch gauge, you will be able to identify the following thread

forms.

American Dyseal Pipe Threads

SAE J476a, NPT, NPSM

American National Screw Threads

SAE J475a, JIC

British Pipe Parallel Threads

ISO/BS 2779-NF EO3-005 DIN 3852 Pg. 2 (Parallel Threads)

British Pipe Taper Threads

BS21-IS07, DIN 3852 (Taper Threads)

Metric Parallel Threads

ISO 6149 DIN 3852

Metric Taper Threads

DIN 3852

Japanese Industrial Standard

JIS BO202 (PF Thread), BO203 Tapered (PT Thread)

How to use the Caliper

The calipers in the kit can be used to help you identify both American and Foreign thread forms,

including internal and external th

The top scale is used to identify all inch threads and the bottom scale is used to identify all

metric threads. When using the scale to correctly determine your thread size, use the first, or left,

line in the window area. See Figure 1 below for cla

To identify external or male threads, use the bottom jaws of the caliper and to identify internal or

female threads use the top jaws of the caliper. See Figure 1 above for clarification.

How to use the thread pitch gauges

All thread pitch gauges in the kit are used the same way in identifying internal or external

threads. Each leaf has a number on it telling you how many threads per inch you have. The only

Identifying Threads



American National Screw Threads

005 DIN 3852 Pg. 2 (Parallel Threads)

IS07, DIN 3852 (Taper Threads)

JIS BO202 (PF Thread), BO203 Tapered (PT Thread)


including internal and external threads.



line in the window area. See Figure 1 below for clarification.



How to use the thread pitch gauges

uges in the kit are used the same way in identifying internal or external









uges in the kit are used the same way in identifying internal or external


exception to this is on the metric gauge. On the metric gauge, the number on each leaf

the thread pitch (distance from the crest of one thread to the crest of the next thread.) in

millimeters. Figure 2 below shows you the proper use of the thread gauge.

One important point illustrated above is the use of the correct thread pitch gauge on the threads.

Incorrect thread identification can cause: equipment failure, leaking connections, thread damage

to mating parts, or possible serious human injury.Additional

throughout this catalog.

General Information

In identifying fittings, you should always be sure to identify both sides of the fitting. Except for

plugs, caps and unions, all fittings grip a rigid tube or a hose and are s

port. Try to divide each fitting into two separate identifying sections

and side B (the port threads).

Identifying the Port Side of Fittings (Side B)

There are six common port threads on fittings. Th

1. British Parallel Pipe Threads

2. British Taper Pipe Threads

3. Metric Threads, Parallel

4. Metric Threads, Taper

5. NPT

6. SAE Straight Threads

Parallel Thread vs. Tapered Threads

To identify any port side thread, first determine if

and/or use of a straight edge. A parallel thread will have some means of sealing at the top of the

thread, either by O-ring, metal seal, or possibly by a machined ring in the hex itself. A taper

thread seals on the threads themselves by wedging into the female port and sealing by thread

contact.

exception to this is on the metric gauge. On the metric gauge, the number on each leaf


millimeters. Figure 2 below shows you the proper use of the thread gauge.



to mating parts, or possible serious human injury.Additional thread identification is explained


plugs, caps and unions, all fittings grip a rigid tube or a hose and are screwed into some type of

port. Try to divide each fitting into two separate identifying sections - side A (grips tube or hose)

Identifying the Port Side of Fittings (Side B)

There are six common port threads on fittings. They are as follows:

Parallel Thread vs. Tapered Threads

To identify any port side thread, first determine if the thread is tapered or parallel by inspection


ring, metal seal, or possibly by a machined ring in the hex itself. A taper

on the threads themselves by wedging into the female port and sealing by thread

exception to this is on the metric gauge. On the metric gauge, the number on each leaf represents




thread identification is explained


crewed into some type of

side A (grips tube or hose)

the thread is tapered or parallel by inspection


ring, metal seal, or possibly by a machined ring in the hex itself. A taper

on the threads themselves by wedging into the female port and sealing by thread

American Tapered Pipe Threads

There are various American Pipe Thread series in use today. Two of the more popular thread

forms used are the Dryseal American Standa

Standard Straight Pipe Thread for Mechanical Joints (NPSM). Unlike the British threads, our

pipe threads have a 60º thread flank angle. See Figure 6. (Refer to

information.)

British Thread Forms

Two of the more popular thread forms used in the world today are the Britis

Tapered (BSPT) and the British Standard Parallel Pipe (BSPP). Both of these thread forms have

a 55º thread flank angle. See Figure 7. The BSPT or BSPP cannot be interchanged with our own

pipe threads due to the difference in thread flank an

The British thread forms use sizes similar to our own pipe threads

determine if the thread is tapered or parallel, then measure it with the thread gauges supplied in

your Thread ID Kit under British thread forms. All

our own NPT for sizing. (A 1/4" BSPT or BSPP thread, if held end to end with a 1/4" NPT will

have approximately the same thread O.D.)

Neither the British Standard Parallel Pipe or the British Standard Pipe Tapered

threads, although many people find these threads "foreign" and conclude that they must then be

"metric".

American Tapered Pipe Threads


forms used are the Dryseal American Standard Taper Pipe Thread (NPTF) and American


pipe threads have a 60º thread flank angle. See Figure 6. (Refer to Chart #3 for additional

Two of the more popular thread forms used in the world today are the British Standard Pipe



pipe threads due to the difference in thread flank angle.

The British thread forms use sizes similar to our own pipe threads - 1/8, 1/4, 3/8, 1/2, etc. First,


your Thread ID Kit under British thread forms. All BSPT and BSPP sizes can be compared to


have approximately the same thread O.D.).

Neither the British Standard Parallel Pipe or the British Standard Pipe Tapered are true metric



rd Taper Pipe Thread (NPTF) and American


for additional

h Standard Pipe



1/8, 1/4, 3/8, 1/2, etc. First,


BSPT and BSPP sizes can be compared to


are true metric


Japanese Threads

The Japanese Industrial Standard (J.I.S.) tapered and parallel threads are the same as the British

Standard Pipe Tapered and British Standard Parallel Pipe threads. In addition to normal BSPP

hose fittings, there are also flare fittings with a 30º or 45º flare in combination with either metric

or BSPP threads that meet the J.I.S. standard. These are commonly called Koma

Mitsubishi fittings.

Metric Threads

Another port thread form found on overseas equipment is the true metric thread. This thread

form is probably the easiest to measure and identify.

First, determine if your thread is tapered or parallel by the same

British Threads Forms Instructions. If you believe you have a metric parallel thread, you can

measure it as follows:

First, measure the outer diameter of the thread in millimeters as shown in the following diagram

using your calipers. (D = 24mm). Next, use your metric thread gauges to measure the distance

from the crest of one thread to the crest of the next in millimeters. (P)

This thread has 1.5 millimeters between threads. Combine the O.D. of the thread measurement

with this second measurement to form a metric thread callout (i.e. M24 x 1.5).

To measure metric taper threads, follow the same instructions as for the metric parallel thread.

Since it will be difficult to measure the O.D. of a tapered thread, measure the O.D. at t

thread from the end. Then use your metric thread gauges as before. The thread callout will be

M24 x 1.5 tapered.

Identifying the Tube (Side A) Side

The end of the fitting that grips a tube must be studied carefully for correct sizing. The first and

most obvious indication is to measure the tube that is being gripped. Place you caliper across the

diameter of the tube and read from the millimeter scale on your caliper. The following sizes are

the most popular metric O.D. tube sizes in millimeters.


ered and British Standard Parallel Pipe threads. In addition to normal BSPP


or BSPP threads that meet the J.I.S. standard. These are commonly called Komatsu and


form is probably the easiest to measure and identify.

First, determine if your thread is tapered or parallel by the same methods employed under the



ipers. (D = 24mm). Next, use your metric thread gauges to measure the distance

from the crest of one thread to the crest of the next in millimeters. (P)


second measurement to form a metric thread callout (i.e. M24 x 1.5).


Since it will be difficult to measure the O.D. of a tapered thread, measure the O.D. at t


Identifying the Tube (Side A) Side


obvious indication is to measure the tube that is being gripped. Place you caliper across the


the most popular metric O.D. tube sizes in millimeters.


ered and British Standard Parallel Pipe threads. In addition to normal BSPP


tsu and


methods employed under the



ipers. (D = 24mm). Next, use your metric thread gauges to measure the distance



Since it will be difficult to measure the O.D. of a tapered thread, measure the O.D. at the third



obvious indication is to measure the tube that is being gripped. Place you caliper across the


4mm

6mm

8mm

10mm

12mm

14mm

15mm

16mm

18mm

20mm

22mm

25mm

28mm

30mm

32mm

35mm

38mm

42mm

The 24° Cone

Probably the single most popular bite-type fitting in Europe is the 24º cone. An EO style fitting

and SAE flareless incorporates a 24º tapered throat angle and the nut drives the ferrule into the

tube as it is tightened during assembly. There are various forms of ferrules that are used, but the

bodies and nuts are all made to standards insuring the interchangeability between manufacturers.

In metric sizes, the 24º fitting is made in six different series, AL series and LL series for low

pressure, L series for medium pressure service, S series for high-pressure severe-service

application, A series for French metric and AG series for GAZ.

To identify metric 24º fittings, first examine the markings on the tube nut itself. Most reputable

manufacturers of metric 24º fittings mark the tube size and the series on the nose of the nut itself.

See Figure #9.

24º Bite-Type Fittings - Measuring the Tube Side Thread

Tube Connections

The cross-section in Figure #10 represents one end of a flareless tube connection without the nut

and sleeve. The thread size can easily be identified by measuring the dimensions as shown in

Figure #8 and the connection tube size can easily be identified by measuring dimension A in

Figure #10.

37° Flared Fittings - JIC 37°

The 37º flared fitting functions by establishing one circular line contact between the nose of the

fitting and the flare of the tube or female seat in a hose fitting. The function of the threads is to

hold the two mating threads mechanically in place. JIC 37º couplings are generally used with

higher-pressure industrial and mobile applications.

SAE 45° Flared Fittings

Sealing characteristics and thread identification is the same as the JIC 37º flared fittings. SAE

45º couplings are generally used in automotive low-pressure systems.

SAE Straight Thread with O-Ring

Straight thread adapters with O-ring into SAE Straight thread bosses seal strictly by use of the O-

ring.

Flat Face Fittings

The BSP and SAE Standard Flat face fittings have an O-ring groove in the male end. The BSP

version is used on Hiab cranes and loaders.

Flange Fittings

The SAE Standard flange face fittings are made in two styles. Code 61 and Code 62. Code 61 is

rated at 3000 PSI and Code 62 is rated at 6000 PSI, in all sizes. Poclain has their own unique

style of flange fittings.

60° Cone (30° Seat) Fittings

In the SAE standards the female pipe swivel and the male pipe ends are said to have a 30º seat.

This angle is measured from the seat to the centerline. In Europe both the British and Metric

versions are said to have a 60º Cone, where the total angle is measured. The U.S. Standard

National Pipe Straight Mechanical (NPSM) female swivel mates with the NPTF male fitting.

Note the male end must have the 30º seat to seal properly.

Ball Nose Fittings

Many manufacturers in Europe and the U.S. manufacture their swivel fittings with a ball nose.

This allows the same component to be used with more than one style male end. (i.e. M12x1.5 nut

on a ball nose swivel might fit both a 6mm Din 20078 24º Light Cone male and a 4mm Din 7631

60º Cone Male.)

Standpipe Fittings

These fittings have a metric tube stub, which will accept an EO nut and ferrule. When the ferrule

is preset on the standpipe they function the same as the DIN swivels in the 24º cone paragraph.

identifying threads

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