 |
| ||||||||||||||||||||||||||||||||
For recessing, cutting-out and cutting-off the end-cut turning tool and hook tool are mostly used.
The end-cut turning tool is used for machining on the circumferential surface. The hook tool serves to machine hollow parts.
Figure 1 Right-hand end-cut turning
tool
1 tool point (or tool nose)
2 shank
Figure 2 Hook tool
1 tool point (or tool nose)
2 shank
What are the main components of an end-cut turning tool?
1.
__________________________________________
2.
__________________________________________
For special shapes of grooves and recesses, the turning tools to be used are ground to suit the shape to be produced.
In order to maintain the shape of the cutting portion and to save cutting tool material, the end-cut turning tool is reground on the cutting face only.
Figure 3 Right-hand end-cut turning
tool
1 side-cutting edge (or primary cutting edge),
2 end flank,
3 shank,
4 cutting face,
5 flank,
6 regrind
When grinding the end-cut turning tool, special attention is to be paid to maintaining the angles.
The following rules are to be observed:
- Length of the cutting portion depends on the depth of the recess to be produced.- Clearance angle and rake angle depend on the material of the workpiece.
- Tapering from front to rear and top to bottom to avoid jamming.
Figure 4 Tapering of cutting edges
(1) from front to rear
(2) from top to bottom
- For cutting-out and cutting-off the primary cutting edge is ground obliquely so that the corner of the edge facing the workpiece is slightly leading. This avoids hooking or breaking off when parting, and no parting-off flash is left on the workpiece.
Figure 5
(1) unfavourable shape of cutting edge
(2) correct shape of cutting edge
In order to guarantee economical machining of large quantities of workpieces, a special grinding angle (roof type) is used for the cutting-off tool which permits the tool life to be increased and high cutting speeds to be used.
- For cutting-out, a special grinding angle is applied to the secondary cutting edge to avoid "dragging".
Re-grinding at the side weakens the end-cut turning tool. It results in high wear and the danger of breaking off.
Figure 6 End-cut turning tool with
roof-type grind
1 cutting relief 0.1 - 0.2,
2 trailing edges 100,
3 flank 12°,
4 tool point 6-8°,
5 tool point 30° x 0.1,
6 cutting face
The special grind is lapped.
Figure 7 Right-hand end-cut turning
tool with special grinding for cutting out
1 primary cutting edge
2 flank
3 special grind
What is to be considered when grinding an end-cut turning
tool?
_________________________________________
_________________________________________
_________________________________________
Because of the intricacy of the recesses and of the constantly changing cutting speed in cutting-off, cutting tools of high-speed steel are normally used since carbide-tipped end-cut turning tools often chip.
Why does the cutting speed constantly change when the cutting
edge of the end-cut turning tool is approaching the
centre?
_________________________________________
_________________________________________
_________________________________________
_________________________________________
 |
 |
