Whitworth thread milling

[HillJack]

I'm challenged with the task of cutting some internal Whitworth threads (British Standard pipe thread) in Delrin. I think I can handle programming it in v8, but I'm not sure what the best tool would be to use- thread mill, threading tool, or like a custom ground double angle milling cutter. The major diameter of the threads is 2" and I only need about a 1/2" of threads. Anyone have any suggestions? HJ

[lovell110]

HJ,

When you say a British Standard Pipe Thread that leaves me with a few questions.

1) Are you referring to BSPT or BSPP

2) What type of machine?

3) Qty of pcs?

Answer these and I'll do what I can for you.

By the way I work for a pipe fitting manufacturer.

John

[gmenzies]

we cut alot of bottle mold threads. ie: buttress sytle. because of where i start and stop. i generate a spline helix the pitch and turns i need and use contour incremental

with perpendicular lead in and out. when the threads exceeds one full turn , turn of infinite look ahead.

with your application in delrin , i made a protoype ( out of delrin)with a iscar off the shelf 60 degree tool (single lip)in one pass

 

 

[HillJack]

Thanks for the response guys.

lovell110, from what I can tell it's a BSPT. I'm using a Haas vertical mill. And it looks like we got 4 pieces to do.

gmenzies, I like the idea of cutting it with one pass, I think my problem now is that the thread is 55 degrees. The off the shelf cutters look to be 60. So, if I'm going to get one ground, I kinda have my choice of which type to use.

HJ

 

[lovell110]

HJ,

The only difference between NPT and BSPT is the thread angle(55 deg,) and number of threads per inch(11). I am assuming you are doing ID threads. If you have a grinding dept. you can grind a new/used top notch style insert. Use a top notch style boring bar for you tool holder in a collet on your mill. If not yu can certainly buy those style inserts from any reputable distributor. Depending on what version of MC you are using you may be able to use the thread milling feature. Rev that baby up and away you go! You will definately want to practice this process before trying it on your customers parts!. Let me know how you make out! This is the cheapest way I can think of for you. Oh! By the way your hole prep is very important too! You can cheat this by using a NPT reamer. The taper angle is the same.

John

[HillJack]

Thanks lovell110 for your help. I ended up using a single flute carbide thread cutter that I had ground to the BSPT spec's. V8's thread milling operation worked great.

HJ