DIYbanter - View Single Post

wrote:
Hello,

First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
lathe was given to me by a friend a few weeks ago and it didn't get
much use at all from him.

For some reason the thread cutting system seems way off. When I cut one
pass (say 16tpi) and measure the light cut with my thread guage, I'm
getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
closer to a 28tpi cut. I've checked and rechecked all of the gear
combinations listed on the chart and the are correct.

Additionally, when I try to use the thread chasing dial, I can never
get the same cutting pass. For example, I'll use strictly the number 1
on the dial and my second cutting pass will be right in between the
first cutting pass. I'll try it for a third pass and I'll get a whole
different cutting pass.

This is really frusterating! Has anybody ever heard of this before? I
was actually impressed with the quality of this Chinese manufacturing,
but now I'm beginning to wonder...

If pictures would help at all I'd be glad to take a few and post them.

Thank you very much,
Carter

I wonder if you have a metric cut lead screw. I would recommend that
you measure the pitch to see if it is cut in inches or millimeters.
That would explain why you cannot pick up the lead on your second cut
using the chasing dial. It may also explain why your threads are off in
that the gearing/lead screw combination may only allow an approximation
of the desired thread. HTH