We have a job that requires an internal thread that is 3"-4x 5" deep. Normally we would thread something like in the lathe but this part is realky hard to chuck. We have a mazak vtc16c cnc mill. Would we have any luck threading these on this mill. If so what kind of tooling would best. The biggest thing we have thread milled is 3/4-10 using a thread mill.
If its only 1 part or a few, I really like using lathe bars with full profile inserts. I do this regularly in 4140 or 4340 for large metric threads, last one I ran was M64 x 4 almost 5" deep. the single cutting edge isnt that slow, and it clears chips really well. Also I like coolant thru bars.
My other option would be Sandvik, but you would need to do a lot of them. They make an inserted thread milling cutter that uses a triangular, tangential insert. have bodies from around 1.75 major upto shell mills. I have 1 on a 3/4" facemill arbor that does large acmes, like 2TPI great. this tool is essentiall a single disc cutter, so cuts 1 pitch at a time.
For really wierd stuff I have had single index milling cutters ground to form, they are designed for old school thread milling on a thread miller, but I mill face mill arbor drive keys in them, and slap em on an arbor. They are only High speed steel, so slow, but for .5 tpi acmes they work awesome.
