[micktg007]

can someone help am having trouble understanding hw to do a internal pipe thread
can somone write me a program as it may help me understand
the thread is as follows
3/8" X 19tpi bstp
have no trouble doing normal parrallel
regards mick

[JohnnyTurn]

Mick,

Your missing the R value no doubt. Do you have the Hardinge manuals. They are the best in the business. Written by American Manufacturing Engineers. Not buy Japaneese computer scientists converted into engrish.

The H manuals taught me. But if you still need help Let me know.

Here is a tid bit:

You must have the 1.47 deg taper bored into the hole first. NPT is very close to your BSPT. The only real difference is the Nominal diameter or the largest Dia. in the taper.

If memory serves the Tangent of 1.47 is .031135 (check that)

So take your nominal diameter of the thread. (.5625) and minus off .031135. That's your x start point. (.5313)

Cut this taper first into the I.D. Then using a simple G92 threading cycle use the R value in the execution line

T0505X.500(CLEARANCE FOR RETURN)
G92X.535Z-.500F.0526R-.031135
X.540
etc.

If I remember correct, R- is for internal, R is for external. (check that)

Mick, I used to cut NPT, BSPT threads all the time. It's been a while since I have done one. Check my figures. I am 99% sure this is good info. I can take a min. on Monday and look at one of my proven programs at the shop.

Good luck!

[teamus]

the tangent is actually .03125 or 1/32 the taper per side per inch or .750 per diameter per ft. And R is negative on an od pipe thread and positive on internal. You are also missing your Z start position of .5.

[JohnnyTurn]

Teamus,

The tangent of 1.47 Deg. is not .03125
It is: .03112 to be exact.

I have not cut NPT in a while so I forgot R- R+ designations.

And since I wrote the code in 2 seconds I did miss my Z Start point.

Check your angle of your workpiece on a optical comparator before it's threaded. That's the only sure way to know if your on the money. Being that close, you are only a half a degree or less off. Doesn't really matter, NPT is a flawed design anyway. On 99% of it's applications, Teflon tape or Pipe Dope must be used to make a perfect seal.

JT

[g-codeguy]

Have only run British straight pipe threads. Here is an example for a 3/8-18 NPT.

X.53Z.2
G76P000129Q30
G76X.639Z-.575P445Q130R.0241F.05556

You didn't say which thread cycle you were using. You should be able to figure out the 3/8-19 BSTP from analyzing this example.