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close this bookThread Cutting by Dies and Taps - Course: Techniques for Machining of Material - Instruction Examples for Practical Vocational Training.
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View the documentIntroduction
View the documentInstruction example 5.1. Spring bolt
View the documentInstruction example 5.2. Ball handle
View the documentInstruction example 5.3. Lance
View the documentInstruction example 5.4. Piston

Instruction example 5.4. Piston

In this example thread cutting is undertaken in blind holes by means of taps.



16 Cr Mo 4 (low-alloyed steel), alloy components: 0.16 % carbon, 1 % chrome, less than 1 % molybdenum, rest iron.


Ø 45 x 93


spiral drill Ø 17.5 mm, machine tap M 20, chucking spanner

Measuring and testing tools

vernier caliper, steel measure


extendable chucking jaws, tap wrench, reducing collars, coolants and lubricants

Required previous knowledge

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

Workshop drawing explanations

M 20:

M = metric thread

All surfaces have been machine-finished.

20 = nominal diameter

Sequence of operations


1. Dimensional inspection

2. Clamp workpiece

Clamping in extendable jaws to Ø 38 mm

3. Clamp tool

Fix spiral drill to tailstock by means of reducing collars

4. Set the cutting values for boring

Spiral drill is made of quick-cutting steel v = 25 - 50 m min-1

5. Undertake a Ø 17.5 x 38 mm bore

Ensure proper cooling. Check bore depth with steel measure on the quill. Debur the workpiece.

6, Set the cutting values for thread cutting

For steel v = 4 - 15 m min-1 heeding the material and thread size

7. Position tap

Select machine tap. Position the railstock tap to centring of tap.

8. Cut the tap

Ensure tap wrench support. Check on proper alignment through the railstock tip.
Keep the chip grooves clean by turning the tap back several times.
Ensure proper cooling and lubrication. Ensure adherence to 30 mm length.

9. Unload workpiece

10. Dimensional inspection