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With the recessing technique the workpieces are machined on the circumferential surface towards the axis of rotation and, in the case of hollow parts, away from the axis of rotation.
Figure 10 Direction of machining when
recessing
1 circumferential surface - towards axis of rotation
2 hollow part - away from axis of rotation
- The part is held in a chuck and for external grooves a live centre is used as counter-support.- The recess in the circumferential surface is turned by a straight right-hand end-cut turning tool or hook tool.
- The workpiece is to be clamped in internally turned chuck jaws to guarantee true running of the workpiece and prevent damage to the surface at the points of contact.
- The width of the recess is produced in one operation provided that the end-cut turning tool or hook tool has the exact width.
Figure 11 Width of recess in one
operation
1 recessing in the circumferential surface
2 recessing in hollow parts
- When recessing thread grooves, grinding of the 60° taper for the thread runout can be done at the same time.- The exact width of the end-cut turning tool necessitates exact sharpening but guarantees dimensional consistency for many parts and is economical.
- To avoid vibrations, the workpiece and end-cut turning tool or hook tool should be clamped as short as possible.
- To ensure proper quality, stop and block gauge should be used.
Due to the rotation of the workpiece to be machined, the diameter of the workpiece is doubled by the amount of feed setting.
Do not do any measuring or testing unless the machine is at rest!
What is to be considered when grinding the round corner for the
chips to roll
off?
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Figure 12 Safe clamping of workpiece
and tool
1 clamping of workpiece
2 clamping of turning tool
Figure 13 Safe clamping of workpiece
and tool
1 clamping of workpiece
2 clamping of turning tool
Figure 14 Round (concave) corner for
the chips to roll off at the end-cut turning tool
1 unfavourable grind,
2 correct grind
For dimensional checks retract the hook tool sufficiently and cover it by a rag to prevent accidents.
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