Pipe threads

[fukeneh]

Not sure where to post this but maybe someone here can help. I am writing a program and the part has 1/4-18-NPT pipe threads. I want to do the threads in the machine. What I need to know is what is the max and min for the hole size. The depth of the hole is .625. I think the bottom (minimum) of the hole is going to be .440 but what is the top of the hole suppose to be? .460?
.455? I want to use the top of the hole diameter i.e. .46 and taper down to the .440. Anyone know what the top of the hole and the bottom of the hole should measure for 1/4-18 pipe threads?


Thanks!!

[DareBee]

Standard hole would be 7/16 straight

[fukeneh]

Originally Posted by DareBee Standard hole would be 7/16 straight

how would you do the threads in the machine? drill the 7/16. then thread?? I need the taper. There has to be a min for the bottom and a max for the top of the hole for the taper. There has to be a way to do pipe threads in the machine.

[mrainey]

Look here for the dimensions of NPT reamers - use them as guidance for your machining.

http://www.sct-usa.com/pt12.asp

[fukeneh]

thanks i'll look into it.

[M-man]

IS this a tapping operation? Just drill a straight hole as amost everyone else does..

[fukeneh]

I want to thread the part in the machine. I don't want to drill 7/16 then take it out and tap it. I want to use a boring bar to get the taper then thread the taper in the machine with a threader. So when i'm done i'll have 1/4-18 pipe threads done in the machine. NOT tapping.

[mxtras]

How do you get a tapered hole with a boring bar? I mean intentionally...

Scott

[fukeneh]

You drill the hole undersize you call up your boring bar then:

G00 X.5 Z0.
G01 X.45 Z-.625 F.002

There, now we have a taper in the hole.

Your missing the whole point of my question. I know how to program but what I dont know is what a 1/4-18 pipe thread would be before threading. What would the taper be. After I drill the hole then bore the taper what should te top of the hole measure and what would the bottom of the hole measure before threading.

[arfonce]

Just googled for it. Taper is 3/4" per foot or 3.576 degrees with the larger end of .540 diameter for a 1/4NPT thread.

[Pete Stenabaugh]

Why bother with all that nonsense, drill the hole to 7/16 and just run a tap in the hole and get on with the rest of the job. It seems senseless to re-invent the wheel for some operations. You can always jog the machine back and forth to break chips if necessary.

Pete

[jbclimbs]

They've got things called thread mills that are pretty keen in doing what you are attempting, but I agree, just drill the damn hole and tap it with a 1/4 npt tap.