E&OE
© 2020 Baumr-AG
36
Screw Cutting
This operation requires a degree of skill and accuracy and should not be attempted unless you are completely
familiar with all aspects of the lathe.
Essentially, the saddle will move towards the headstock under power, the same as cutting using auto feed,
except the rate of feed is greater, as determined by the gear configuration. The cutting tool, therefore, is moving
ever closer to the rotating chuck. Great care and concentration must be exercised to ensure that the two do not
meet when the machine is operating, as the possible damage caused could be disastrous.
The lathe is supplied with a leadscrew that will produce Imperial Threads in a range from 12 to 52 threads per
inch or metric threads in a range from 0.4-2.0mm pitch. It is important to remember that the type of thread you
need to cut, i.e. UNF, BA, BSP, BSW etc., will be totally dependent upon the cutting tool profile, as profiles differ
from thread to thread.
For detailed information regarding screw cutting techniques, cutting tools etc., you should consult a suitable
handbook or obtain advice from a qualified person.
The general procedure for screw cutting is as follows:
24. Try to get as much distance from the chuck to the end of the proposed screw thread as possible, and if your
design allows, cut a 'run-off' into the workpiece which is of a smaller diameter than the root diameter of the
proposed screw thread.
NOTE:
For long threads, it may be necessary to use 'steady’s' (see
25. Install the appropriate gears for the thread required, and correctly mount the cutting tool. Set your required
depth of cut and position the tool ready to begin cutting.
NOTE
: Depth of cut is vitally important and may be calculated or obtained from an appropriate reference
manual.
26. Take all necessary precautions previously stated and start the machine with the automatic feed lever in its'
disengaged position (UP).
27. Engage the auto-feed lever sharply, turn the FORWARD/OFF/REVERSE (F/O/R) switch (C) to 'FORWARD'.
As the tool approaches the end of the desired thread, turn the switch (C) to 'OFF'. Do not disengage the
auto-feed lever.
28. Retract the tool, using the cross-slide feed handle, noting the exact position on the scale and the exact
number of turns.
Turn the switch (C) to 'REVERSE', the saddle winds back to the beginning and turn switch (C) to 'OFF'.
Reset the tool by winding IN the cross-slide the exact number of turns previously wound OUT and then
continue to wind IN the to the desired depth of cut.
29. Repeat steps 4 and 5. Proceed in this manner until the thread is completed.
