Toolpost bolt hole threads?

"WHY IN THE WORLD DO THEY SELL LATHES WITH THOSE 4-WAY TOOLPOSTS?"
Because they are basic and cost less. One of the lathes at work has a 4 way thats 10" square, a 2" boring bar resides in it permanently.

Can you imagine the size of the QCTP for that size? Let alone the cost.
I noticed you didn't chamfer the end of your bolt prior to threading in the top photo. May I suggest you do that in future because it looks nicer and it is a transition point for the insert whereby it doesn't get hammered by being forced into a 90 degree edge. Overall a job well done and in stainless too.
 
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Oxtool has made a video about this subject, called:
Metric Threading with an Inch Lead Screw

I cant add links yet, because i'm new here.
I mostly do metric threading, with an imperial leadscrew. But I dont have an threading dial yet, so cant use this trick unfortunately.
 
"WHY IN THE WORLD DO THEY SELL LATHES WITH THOSE 4-WAY TOOLPOSTS?"
Because they are basic and cost less. One of the lathes at work has a 4 way thats 8" square, a 2" boring bar resides in it permanently.

Can you imagine the size of the QCTP for that size? Let alone the cost.
I noticed you didn't chamfer the end of your bolt prior to threading in the top photo. May I suggest you do that in future because it looks nicer and it is a transition point for the insert whereby it doesn't get hammered by being forced into a 90 degree edge. Overall a job well done and in stainless too.

You're right . . . I didn't chamfer first. I usually do; but had so many failed attempts that I forgot. If it had any problems starting into the threaded hole, I was going to chamfer afterwards. But the threads started easily every time.
I was wondering what flaws in my work would be noticed; and welcome all advice and constructive criticisms.

Ken
 
Ken, Considering your work was with stainless, it looks fairly good for a first attempt. Looking at your second photo which is the clearest I can see faint chatter marks. Not a serious issue unless its a production run.
Feeding in square on will produce this amongst other factors. Feeding in at 29.5 deg may have eliminated it. Its a good job, nothing to worry about, don't forget practice makes perfect.
 
Ken, Considering your work was with stainless, it looks fairly good for a first attempt. Looking at your second photo which is the clearest I can see faint chatter marks. Not a serious issue unless its a production run.
Feeding in square on will produce this amongst other factors. Feeding in at 29.5 deg may have eliminated it. Its a good job, nothing to worry about, don't forget practice makes perfect.

Thank you.
I actually did feed with the compound set at about 29 degrees so the tool only cuts into one side of the thread. I can see the result of the chatter, too. I had the workpiece as close to the chuck as I dared, but didn't use a center to hold the free end. That might have helped.
Yeah, I could use some more practice; and I'll get it as I work with the new lathe. I've had a 12x36 for almost 15 years. This new lathe is a bunch more substantial and a heck of a lot of fun to use.
 
Thank you.
I actually did feed with the compound set at about 29 degrees so the tool only cuts into one side of the thread. I can see the result of the chatter, too. I had the workpiece as close to the chuck as I dared, but didn't use a center to hold the free end. That might have helped.
Yeah, I could use some more practice; and I'll get it as I work with the new lathe. I've had a 12x36 for almost 15 years. This new lathe is a bunch more substantial and a heck of a lot of fun to use.

Stainless is a pain to work with sometimes, its soft but tough at the same time. On smaller diameter stuff I always try to use a center (live or dead) to prevent chatter.
Keep up the good work.
 
That's when I learned something else new.
My lathe will do SAE threads all day long using the threading dial. But no such dial for Metric. ... I'll just reverse the feed and back up.


Not just your lathe. Every lathe. Either the leadscrew is spaced for inches or for metric. You don't get both, unless you put a god-awful amount of gearing in the apron to convert one to the other.
 
My lathe will do SAE threads all day long using the threading dial. But no such dial for Metric. I finally figured out what the placard means, "For Metric, the Half-Nut nut must stay engaged." HUH? But now I get it. The feed screw is SAE; so the threading dial will only indicate SAE threading. (I think that's right)

The big difference in metric pitch and unified national (inch) "tpi" is that
there's almost always an integer number of identical threads per inch. So a threading dial can
tell you for sure that the engagement is at exactly +/- N inch from the start,
then the half-nut will engage and travel to the partly-cut thread.
For even threads (6 tpi or 32 tpi but not 27 tpi) it will also do this at
exactly 1/2 inch, so you can use another number (evens or odds only) on
the thread dial... the threading screw is 8 per inch, typically.

If your need is for 10.5 threads per inch, your thread dial isn't much help.

But, standardized metric pitches (M4 x 0.7mm, M12 x 1.75mm, etc.) don't
exactly divide (with no remainder) into 1.0 cm, so the whole system is incompatible
with the threading dial trick.

It would take a dial with a quickchange gear cluster, and a table of which to use...
Actually, now that I think of it, a digital readout could be arranged, it'd be
easier than a gearbox. Still wouldn't work with an inch threadscrew, though.
 
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You all talking about MM's made me drag this out!

MMPitchGauge.jpg
But if i had a lathe right now.. i would like to have to have the QCTP myself..
 
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