Threading max diameter

[Maplehead]

Hi All
Does threading on the lathe cause maximum diameter to increase?
I'm guessing yes as I'm pretty sure the 3/8" 16TPI bolt I was making got wider.
Also I imagine as the bit threads it's "pushing" out the teeth.

 

[Flyinfool]

The lathe should not make the major diameter grow. The only way it does is if your tool is dull and is raising a burr. Once you deburr, it will be back down to where it started.

 

[benmychree]

One generally deburrs threads cut in the lathe with a file before trying to gage it with a nut or whatever, such as a thread ring gage or a thread mike.

 

[SLK001]

Since you thread at a low speed, some metals have a tendency to tear (and leave burrs all over the place). Get a triangle file and use it to chase the threads, then a flat mill bastard file to smooth the tops of your threads. Do this until a piece cloth doesn't catch on your threads, then test fit.