npt threads

[scubasteve]

hi can anyone give me an example of a 4 inch npt thread program for fanuc. thanks

[wjbzone]

Are you turning or milling the threads? Also are they ID or OD?
Bill

[scubasteve]

i'm turning the thread on the od. i'm using a single line G76 but i have no data on npt threads.
thanks

steve

[HuFlungDung]

You don't have Machinery's Handbook? Shame, shame

The taper of all National Pipe threads is 3/4" per foot on the diameter, which translates into .0625" change in X for every inch of Z travel.

The effective thread length for 4" NPT is 1.300 inches. Supposing you begin .2" in front, the amount of taper in 1.5" is .09375", which is the amount you would use in your G76, and here I'm guessing, parameter "I" would be either .0469 (if I is a radial value) or else .09375 if it is a diametral value.

The pitch diameter at the beginning of the external thread is 4.33438". This can be measured using the "two wire method", if you are accustomed to using Peedee wires to check.

FYI, All pipe threads from 2.5" pipe on up, are 8tpi.

[Gunner]

Sorry Scuba Steve,
I was out for a couple of days. Here is the format we use for OD NPT threads. You can use Hu's info above. This example is for a 1" - 11 1/2 NPT.

T0900G97S1800M03(THREAD)
G00G40X1.375Z.3T0909
G76P020160M08
G76X1.1219Z-.60R0.0231P570Q130F0.08696M24
Z0.3
G00G28U0
Z1.0
M05
M01

[scubasteve]

thanks to all it really helped

[mtlmnchr]

Hey Scuba, anytime you need something just give me a shout I would be more than happy to help anytime ...goes for anyone else out there also.

[M@T]

I've been doing NPT threads recently which is a bit of a bar steward as the relevant info isnt in the Metric Machinists Handbook.

Bloody yanks

[mtlmnchr]

prolly because npt are National (american) Pipe Threads . Metrics would be BSPT or British Standard Pipe Threads

[HuFlungDung]

AFAIK, I don't think the metric system even knows about any kind of taper pipe threads. Straight pipe yes, tapered, no. And that, ladies and gentlemen, is why the Imperial measurement system is superior

But, I could be wrong.

[M@T]

Originally posted by HuFlungDung But, I could be wrong.

Yeah, you are

We have the BSP (British Standard Pipe) and also a tapered version of it, the BSPT (British Standard Pipe Taper)

Imperial, Superior ?? Hahaha #

The Metric programming system on a Fanuc uses a 3/3 format. 3 digits before and after the decimal point. As far as i'm aware the Imperial system uses a 3/4 format. The 4th digit on the imperial system represents a Tenth of a Thou which is 2.54 microns whereas the 3rd digit on the Metric system represents 1 micon making our system 2.54 times as accurate

[HuFlungDung]

Isn't it funny how all those "metric pipe threads" are so and so many threads per inch, in whole numbers?