41
For the reason of the power at the turning chisel take care that the tool is short and fast fixed.
If the lever arm is to long the turning chisel curves and springs back. The cutting part enters
uneven into the workpiece and is producing a waved surface.
Take care that the turning chisel is placed on the middle of the turning piece.
The control of the height position of the middle of the workpiece is done with the live lathe
center in the tailstock.
For the regulation of the height position of the turning chisel use with straight sheet steel
pieces.
10.2
Thread cutting and automatic feed
10.2.1 Thread
cutting
The thread turning chisel is a form turning chisel with the profile of the thread to be cut. It is ground
according to jigs (diagram 1) and must be adjusted exactly to the middle of the workpiece as, oth-
erwise, the profile of the thread would be distorted.
In order to obtain the correct position of the flanks of the thread to the axis of the workpiece, the
grinding jig is put against the work piece and the turning tool is adjusted in accordance with it.
The feed of the thread turning chisel is affected via the leadscrew, and must correspond to the
thread pitch. The gearwheels in the accessories establish the connection between the feed gears
and the leadscrew. By fitting different conbinations of gearwheels it is possible to cut metric and
inch RH and LH threads. The different axis distances of the toothed wheels can be adjusted by piv-
oting the cutting edge and adjusting the cutting screws.
The feed is switched on by hand on the cam box. When cutting thread, please make sure that the
feed remains continously switched on so that the turning chisel always goes back to the same po-
sition when carrying cut several cuttings. For this reason, when the cutting is finished, the turning
chisel is disengaged from the cross slide because otherwise the flanks and the cuts would be dam-
aged. The chisel is taken back to ist home position via the reversing switch by means of a change
of direction of the motor. It is advisable to cut a 4-5 mm wide groove on the thread end in order to
be able to disengage the threading tool better.
In the case of a long thread diameter, the lathe centre should travel along with the cutting head in
order to avoid the workpiece from being pushed to one side.
Diagram 1: Setting the thread turning chisel
90°
10
.
Applications
10.2.2
Application of change gears
