Thread cutting help

Just for fun

Just for fun

Tim Young
H-M Lifetime Diamond Member
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Oct 7, 2020
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So today was the second time cutting single point threads on my lathe, second time ever cutting threads really. They didn't turn out to good. I'm not positive of the problem, I suspect I was taking too large a cut. And at that point it was too late to get them cleaned up.

I need more practice for sure. I would like to make some M10x1.50 studs. I'm sure I can find something by googleing but does anyone have a favorite link or pdf file for the major and minimum dimensions for metric bolt cutting?

Tim

Photos of todays project.

20220316_174205_copy_1512x1512.jpg

20220316_174417_copy_1512x1512.jpg
 
Yeah, I have thought of that. I guess I should buy a newer one. Mine is dated 1959 and doesn't have any metric stuff in it.

Tim
 
Looks like poor threading tool geometry. Depends somewhat on if you use the cross slide or tool post slide and possible you have the angle wrong. I just did some left hand metric M10-1.5 threads, I usually do a DOC increasing 0.01" per pass, as I get closer to target a 0.005" or to target and then one spring pass. I use the cross slide to advance the cutter using AG60 laydown Carmex inserts, with HSS you may need to be a little less aggressive depending on the material. Stainless will work harden so you need to remove sufficient material on each pass. I zero my dial and use it to advance the cutter and keep track of the DOC each pass, doesn't matter if it is imperial or metric, you are just cutting metal. You will need cut deeper than the minor diameter of the thread pitch if reading the dial or DRO, as cutter will not cut the exact depth you expect. On the M10 the minor diameter was specified as 8.16mm and I ended up at closer to 8.00 on my DRO. You need to have the correct major diameter and also helps to lightly file the thread peaks. You cannot disengage the half nut when doing metric threads, other limitation you may have is going too slow will tear the metal as oppose to cutting it. Also check that your thread cutter is parallel to the chuck.

Thread chart attached gives an approximate DOC per pass. First pass can be deeper if you do not need to do a scratch pass.

TR knowledge base | Thread geometries

Fastener thread geometries, dimensions and tolerances: pitch diameter, major diameter, minor diameter.
www.trfastenings.com

Factory right hand and single pointed left hand M10-1.5 thread, bolts are steel Grade 12.9. Thread is before cleaning with a wire brush. You want to put a small tapper on the end of the bolt and also have minimal stick out to prevent flexing. Another approach I sometimes use is to cut 95% of the thread single point and then do final sizing with an adjustable threading die as need for tight tolerance along the thread and to the female thread.
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Attachments

  • Threading Tool Speeds & Feeds.pdf
    465.3 KB · Views: 16
I use this website as my go-to page for Imperial thread mins and maxes. There's a metric version only a click away. Looks like it's the same site as @devils4ever uses.

Also, to show your threads, a close-up photo in full profile is needed.
 
Material type makes a huge difference also. Trying to learn threading on a chunk of 1018 can be very frustrating. Get some 12l14 and see the difference.
Oh, and it takes some practice.
Joe
 
Have the 17th edition of Machinery's Handbook (1964). There's only 1 page in it on standard metric threads. Apparently at that time, the British, French, German, and Swiss disagreed on Major and Minor diameters! Pitch diameter was consistent, though. Since then, there has been some harmonization.
 
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