Cutting Metric Threads

ronboult said:
The reason that I asked the Q. is that my reading on the Web didn't provide a definitive answer. My current lathe (Sieg SC4) is fully metric but doesn't have a thread dial so I can't just try it. From reading the replies it appears that the answer is not straight forward.
Ron
Click to expand...

Hi Ron

Don't give up on your lathe, it is actually straight forward, your only option is to engage the split nut and leave it engaged throughout the threading proses, at the end of your thread back off the cross slide do not disengage the splitnut, reverse the machine until your back to the beginning of the thread, advance your cross slide back to position you where at plus the depth of your next cut, repeat until finished, if you need to pick up the thread again for whatever reason use a combination of the cross slide and the compound slide.
 
Like everyone else I also thought the halfnuts/threading dial could not be used when single pointing metric with an imperial leadscrew (& vise versa). That is until I came across the following method. Just have to get used to remembering that you are cutting a metric thread & not to loose the exact position on the thread dial. Before this I used to use the foot/spindle brake when threading metric to a close shoulder.

http://conradhoffman.com/metricthreading.htm (9th section down)

 
Thanks for posting that Will. I am anxious to try that now when I get my new lathe.

Mike.
 
Hi Will
Many thanks for posting that link. Great information.

If I understand the technique it should also work cutting both Metric & Imperial threads on a lathe with a Metric Leadscrew like my lathe.

Also I think that a thread dial with any gearing would work.
My current lathe does not have a thread dial so I will have to adapt one.

cheers
Ron
 
That's simple enough. Thanks for passing that along, Will.
 
Hi DonB

Thanks for your reply

The method you describe is actually what I currently do.

The reason I originally asked the Q is that I am considering replacing my current lathe because of a chuck fitting problem and was interested to know if a Thread Dial was any use cutting threads on a metric leadscrew lathe.

Cheers
Ron
 
There is a video on U tube called "threading on a metal lathe without a threading dial." I think this method would work with metric threading as well. Just a thought. good luck.
 
Howdy Guys,Very interesting thread. I also have an "all metric", (3mm leadscrew, 2mm cross slide and compound feedscrews) Asian BV20 lathe that came without a threading indicator.I don't have a problem with reversing the lathe at the end of the cut, but I would like to know if this will not negatively affect the motor. Mine is still the original 220V AC reversable motor.During the last threading operation the motor made funny noises upon reversing and I got a little worried.Greetings from Dark Africa
 
darkzero said:
Like everyone else I also thought the halfnuts/threading dial could not be used when single pointing metric with an imperial leadscrew (& vise versa). That is until I came across the following method. Just have to get used to remembering that you are cutting a metric thread & not to loose the exact position on the thread dial. Before this I used to use the foot/spindle brake when threading metric to a close shoulder.

http://conradhoffman.com/metricthreading.htm (9th section down)


[video=youtube_share;HXt4TWa382Q]http://youtu.be/HXt4TWa382Q[/video]
Click to expand...

Thanks Will
So simple once someone shows you how. Wish I'd known last week when I was doing metric treads.
Live and learn.
Jim
 
Yup, no problem Jim, glad to share. I really like this method!
 
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