Tapered ThreadMilling

[Randy Morton @ Clem Industrial]

This is more of an after point to threadmilling.

 

I want to threadmill a 2.375" VR (NPT) internal thread. I have a bore dia. of 2.100" +.03. This is not the point at which I would chain from tho, other wise I will end up with a D (on the control) of .1 or more.

 

Is there someone or somewhere that I can get the information for the proper circle size to draw for different NPT (or tapered in general) sizes so that, in all hopes my D's come out to either 0.0 or only a couple thou...?

 

Thanks!

[Gary]

I ran some 2" npt last weekend. The bore is going to be 2.188 for the start I tapered at 1.79° to a dia of 2.24 at start of hole. I went .75 dp and helixed up and out. I drew my dia hole at 2.31 to start at and had to comp out about .05 for good fit. Next time I will drow bigger so not so much comp. I used a single flute mill and the pipe od was 2.375.

htp

 

Gary

[doyleg]

Experiment with it and find out what size to make it. Draw a circle then apply your thread toolpath. After running and finding out what your offset was. Change the dia. of the hole to correspond to zero offset. Then export as an operation and save geometry with it. Then when you import your newly created operation, it will have the correct hole size already with it.

[Randy Morton @ Clem Industrial]

The problem with experimentation is that we are a production shop typically we have very little time to mess around 'trying' to get things right. Obviously it's preferable that it is very accurate when the program hits the machine....