threading

[wrenchcruncher]

I bought a new 14x40 metal lathe a year ago and t tried to do my first threading job on this machine, a thread of 13 tpi. The thread turned out uniform & clean but my pitch guage won't fit uniformally, it looks like it isn't cutting 13 tpi but more like 12.5 tpi ?. I know the gearing & speeds are correct. any ideas would be appreciated.

[jackson]

what setting on your dial are you using

[wrenchcruncher]

I tried useing #1 consistantly and it still did the same thing.

[jackson]

try using 3 some lathes iv worked on do better on a differnt setting

[wrenchcruncher]

Thanks I will try it. Have you ran into this same problem?.

[jackson]

oh yes iv acualy had a lathe that you had to start the feed let get to the end of the thread then hand wheel it out and let it feed back because it would not repeat

[Willbird]

As long as you follow the directions for the thread dial it should not matter what NUMBER you engage on. IE many will say something like "Even numbered threads any line, odd numbered threads any numbered line...fractional threads the SAME line every time" Especially if you hit the line every time and the thread followed every time, choosing another line on the thread dila will do nothing different.

I do know that SOME lathes do have a change gear inside the end of the machine that you must swap to get metric threads....maybe that is not setup properly.

I also saw a lathe that had just ONE thread lead out of all of them that was not correct, it was some inexpensive czech lathe or such. An easy one to check without cutting a full thread is 8 TPI, just run a scratch cut deep enough to see, and use a ruler to count the threads in 1"....or just look to see if they all hit the 1/8 lines :-)....4 and 16 are also easy to do the same thing with. For other threads I will usually do the same scratch cut and set my dial calipers to the distance 4 threads should cover, and then measure from scratch to scratch and see if there are 4 threads properly fitting in there.

Bill

[jackson]

Originally Posted by Willbird As long as you follow the directions for the thread dial it should not matter what NUMBER you engage on. IE many will say something like "Even numbered threads any line, odd numbered threads any numbered line...fractional threads the SAME line every time" Especially if you hit the line every time and the thread followed every time, choosing another line on the thread dila will do nothing different.Bill

your right it shouldnt matter but somtimes it does, trust me i'v been there and its a pain in the a$$ but some lathes are like that (mostly come acrossed it in older ones) and the gear is one thing, good call

[Kiwi]

Is your lathe a imperial lathe (lead screw, cross and compound dials.)?
If it's a metric lathe you need a gearwheel with 127 teeth to convert to imperial.
I have a metric lathe which dosen't have a 127 gear and when cutting imperial threads the TPI are not exactly correct.