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With this technique attention is to be paid to the following:
- The workpiece is held in a chuck with live centre as counter-support.- Depending on the state of machining of the parts, chucking is either in hard or in soft chuck jaws.
- The knurling wheels are fixed in the holder by unhardened steel pins.
- The knurling holder is to be clamped (approx. 1 mm) below centre and at right angle to the workpiece axis.
- The matching edge bearing of the tool must be properly located.
- By operating the cross-slide screw, the tool is pressed against the workpiece.
- The tool slide is laterally moved step by step or the longitudinal feed is used.
- The feed must comply with the spiral-knurling pitch to avoid overlapping.
- The tool must not be immediately applied to the full width.
- If possible, the knurling should be produced in one feed setting. For hard materials re-pressing will sometimes be necessary. In such cases the tool is not to be retracted but to continue in the same grooves to avoid overlapping.
- Basically the operation must not take longer than necessary since the cold forming process makes the material harder and more brittle.
- Good cooling and lubrication are to be ensured.
- The workpiece is to be chamfered after knurling.
- Measuring and testing is first by means of the vernier caliper, followed by visual inspection of the knurled portion.
Figure 20 Spiral knurling of long
parts
Figure 21 Spiral knurling of a wide
portion with longitudinal feed
1 workpiece (long)
2 spiral knurling tool
3 pressing of tool
4 weed of tool
Figure 22 Tool not to be applied
immediately to the full width
1 tool
2 workpiece
How are knurling tools
constructed?
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Which types of knurling do you
know?
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Explain the process of spiral knurling of wide
portions!
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