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Anonymous
en respuesta a: Anonymous

I don't do much thread milling so it's mostly an experiment every time to get all the numbers and dimensions correct.

A tapered pipe thread is even more difficult to machine correctly and I would never expect the first one to come out exactly the way you need it.

 

 

There are multiple possibilities for an incorrect thread size: Bad numbers in the thread dimensions/definition but it could also be the tool diameter or tool length.

 

I don't know how FeatureCAM comes up with 23.127 or 24.577mm as a pilot hole. The chart below has 59/64 inches as a pilot hole (=23.416mm).

 

http://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html

 

According to this chart you should mill 10 revolutions of thread which is about 18.14mm deep but to start I would back-off the tool length offset by 9.07mm (=5x thread pitch) and cut only 5 threads. Increase the diameter comp until the thread gage (or mating pipe) goes into your thread 2-3 turns then you can go to full depth and do a little more "fine tuning".

 

...hope it helps but maybe someone else with more thread milling experience has a better method.

F.