Thread milling ACME thread.

[BBprecise]

Got a titanium part with a modified ACME thread and the only way to machine the thread is to thread mill it. The problem is the tool needs to stick out 5-1/4" from the holder. I've been contemplating having the tool made a little thin to reduce cutting pressure. Would just have to step down/up to get it to correct width.

 

Anybody tried doing this and is it a good idea? Or am I pipe dreaming again.

 

The cutter dia. is 1-1/8" with a 3/4" shank. Solid carbide. PD tol. is +/-.0045, but the Z location (for lack of better term) has a +/-.0015 tol.

 

The part is the front block of an M240 machine gun, and the thread is for the barrel. It uses a pin as an anti-rotation stop hence the tight axial location of the thread.

 

Thanks.

[crazy^millman]

Advent Tool holder, Carmex and some others come to mind. Advent makes a skipped tooth design.

[BBprecise]

Part only has 3 threads roughly so I was thinking about a single tooth cutter with multiple flutes. Just not sure if having the tooth ground a little narrow and stepping up/down is a good idea.

 

The major dia. is +/-.005 (internal thread), so if the tool isn't ground correctly I may have a hard time getting the thread to gage correctly. Then again the PD and major dia. have same tolerance so maybe that's a mute point.

 

Tool pressure is biggest concern and a narrower tooth should help with that. I've used a narrower insert on a lathe before to reduce chatter, but never tried it on a mill. Should be possible shouldn't it?

[Matthew Hajicek - Singularity]

Make sure the cutter grinder allows for the flank angle change produced by the helical motion of the cutter.