turning 3 nm27. screw threads there are 4 basic thread forms vee threads buttress square ...

Turning 3Turning 3

NM27NM27

Screw ThreadsScrew Threads

There are 4 basic Thread FormsThere are 4 basic Thread Forms

Vee ThreadsVee Threads ButtressButtress SquareSquare TrapezoidalTrapezoidal

Screw ThreadsScrew Threads

Vee ThreadVee Thread

Screw ThreadsScrew Threads

Buttress ThreadButtress Thread

Screw ThreadsScrew Threads

Square ThreadSquare Thread

Screw ThreadsScrew Threads

Trapezoidal Thread (30Trapezoidal Thread (30° Angle)° Angle)

Screw ThreadsScrew Threads

Thread TerminologyThread Terminology

PitchPitchDistance from a point on one Distance from a point on one

Thread Groove to the exact Thread Groove to the exact same point on the next Thread same point on the next Thread GrooveGroove

Screw ThreadsScrew Threads

Thread TerminologyThread Terminology

LeadLead

Pitch x Number of StartsPitch x Number of Starts

Screw ThreadsScrew Threads

Thread TerminologyThread Terminology

StartsStarts

Grooves running side by side Grooves running side by side on the same cylinderon the same cylinder

Screw ThreadsScrew Threads

Lead = 12 Lead = 12 Lead = 6Lead = 12 Lead = 12 Lead = 6 Pitch = 3 Pitch = 6 Pitch = 6Pitch = 3 Pitch = 6 Pitch = 6 Starts = 4 Starts = 2 Starts = 1Starts = 4 Starts = 2 Starts = 1

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How many Starts?How many Starts?

21

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How many Starts?How many Starts?

32

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How many Starts?How many Starts?

3 4

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Job 1Job 1

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Alternative to Angling Compound SlideAlternative to Angling Compound Slide

Compound Slide moves = ½ Cross Slide Movement

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Methods of Testing ThreadsMethods of Testing Threads

Test NutTest Nut

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Methods of Testing ThreadsMethods of Testing Threads

Go – No Go Thread Caliper GaugeGo – No Go Thread Caliper Gauge

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Methods of Testing ThreadsMethods of Testing Threads

Three Wire MethodThree Wire Method

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Three Wire Method requires Three Wire Method requires calculating:calculating:

Best Wire Size = Best Wire Size = P

2 x Cos 30º

(ie. ½ included angle)

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Three Wire Method requires Three Wire Method requires calculating:calculating:

Measurement Over Wires = Measurement Over Wires =

M = D – 1.5155 x P + 3 x W

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External ThreadsExternal Threads

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Full Form Carbide InsertFull Form Carbide Insert

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Internal ThreadInternal Thread

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Tracking RatioTracking Ratio

Tracking Ratio =Tracking Ratio =

Usually expressed as the lowest whole Usually expressed as the lowest whole number rationumber ratio

Eg. Eg. == 1 = Magic #1 = Magic #

Lead of WorkLead of Work

Lead of Lead ScrewLead of Lead Screw

11

22

33

66

(The Magic # is used to (The Magic # is used to determine the determine the

Starwheel or Chaser Starwheel or Chaser Dial details)Dial details)

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Tracking RatioTracking Ratio

Tracking Ratio =Tracking Ratio =

Usually expressed as the lowest Usually expressed as the lowest whole number ratiowhole number ratio

Eg. Eg. == 5 = Magic #5 = Magic #

Lead of WorkLead of Work

Lead of Lead ScrewLead of Lead Screw

1.251.2566

55

2424

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Tracking the ThreadTracking the Thread

Tracking the Thread means to engage Tracking the Thread means to engage into the same Thread groove on into the same Thread groove on successive pass of the tool.successive pass of the tool.

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Methods of Tracking the ThreadMethods of Tracking the Thread

StarwheelStarwheel Chaser DialChaser Dial Reversing the MachineReversing the Machine Repeat Distance MethodRepeat Distance Method

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StarwheelStarwheel

A thin gear like disc with teeth cut of a A thin gear like disc with teeth cut of a size to engage with the Leadscrew of size to engage with the Leadscrew of the Lathethe Lathe

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Chaser DialChaser Dial

Sometimes used in conjunction with a Sometimes used in conjunction with a Starwheel to assist correct engagement Starwheel to assist correct engagement of the Leadscrewof the Leadscrew

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Chaser Dial DetailsChaser Dial Details

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Reversing the MachineReversing the Machine

Reversing the Spindle is useful where a Reversing the Spindle is useful where a Thread with an unusual Lead needs to Thread with an unusual Lead needs to be producedbe produced

Usually achieved by reversing the Usually achieved by reversing the direction of the Lathe spindle without direction of the Lathe spindle without disengaging any of the drive gearsdisengaging any of the drive gears

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Repeat Distance MethodRepeat Distance Method

Repeat Distance is calculated by Repeat Distance is calculated by multiplying the Tracking Ratio by the multiplying the Tracking Ratio by the Lead of the LeadscrewLead of the Leadscrew

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ThreadsThreads

Metric Threads Metric Threads available by direct available by direct selectionselection