Thread Cutting by Dies and Taps - Course: Techniques for Machining of Material - Instruction Examples for Practical Vocational Training.: Instruction example 5.3. Lance

Thread Cutting by Dies and Taps - Course: Techniques for Machining of Material - Instruction Examples for Practical Vocational Training.

		(introduction...)
		Introduction
		Instruction example 5.1. Spring bolt
		Instruction example 5.2. Ball handle
		Instruction example 5.3. Lance
		Instruction example 5.4. Piston

In this example particular attention is given to practising thread cutting by tap on through holes.

Figure

Material

35 Cr Al 6 (low-alloyed steel, alloy components: 0.35 % carbon, 1.5 % chrome, 1 % aluminium, rest iron)

Dimensions

Ø 52 x 87

Tools

bent right internal roughing lathe, clamping spanner, one set of hand taps M 30

Measuring and testing tools

internal thread gauge M 30, vernier caliper

Accessories

extendable chucking jaws, tap wrench, coolants and lubricants

Required previous knowledge

drawing comprehension, measuring and checking, thread cutting by hand, centring, boring, counter-boring

Workshop drawing explanations

M 30:	M = metric thread	All surfaces have been machine-finished.
	30 = nominal diameter

Sequence of operations	Remarks

1. Dimensional inspection

2. Clamp workpiece	Clamping in extendable chucking jaws. Ensure true running.

3. Clamp tool	Use prismatic base as lathe has a round shank.

4. Set the cutting values for boring

5. Yield thread Ø M 30	Bore to Ø 26.7. Material is compressed during thread cutting resulting in a bore diameter decrease. Debur 2 mm x 45°!

6. Set the cutting values for thread cutting	For steel v = 4 - 15 m min¹according to material and thread size

7. Position tap	Select manual tap. Position the railstock tip to centring of tap.

8. Cut the tap	Sequence - entering tap, plug tap thread, plug (third) tap. Initially use the plug tap and plug (third) tap to undertake several turns by hand so that the tap sets to the prenotched thread. Ensure tap wrench support. Keep the chip grooves clean by turning back the tap several times. Ensure proper cooling and lubrication. Indicate possible accident hazards 1

9. Unload the workpiece

10. Dimensional inspection

Lance