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Coupling (half) O.D. Tolerance

Coupling (half) O.D. Tolerance

Coupling (half) O.D. Tolerance

(OP)
Looking for information on the outside diameter dimensions and tolerances for 150 lb half couplings. I currently recieved some 1/2" NPT half couplings from my supplier that had an OD that measured .960". I complained about it but the supplier said it is typical to have large fluctuations in the OD of couplings. I know the nominal OD of a 1/2" NPT half coupling is 1.063". I also use 3000 and 6000 lb couplings, so eventually I am sure this information will come up on these larger fittings as well. Anyone know where I can find this information? Any help is appreciated.

Thanks,

RE: Coupling (half) O.D. Tolerance

AA;
I think you want ASME B16.11.  I'm not sure if you'll find tolerances for coupling OD's.  You may have to work of off wall thickness.

RE: Coupling (half) O.D. Tolerance

(OP)
Thanks,

I believe B16.11 applies to forged fittings, which in the couplers case is 3000 lb and up. Also, calculating the minimum OD based off of minimum wall thickness can be a little tricky to work with, since the maximum major diameter of an internal NPT thread is not clearly defined. I suppose I could take E1 plus the max thread height (.057) from machinery's hand book and assume that is the maximum major diameter. For a 1/2" NPT thread, that puts the max. major at .836". Now if I could find what the minimum wall thickness of a 150 lb half coupling is, than maybe I can come up with a reasonable number for the minimum OD of said coupling. Thanks for looking.

RE: Coupling (half) O.D. Tolerance

(OP)
Pennpiper,
"150 lb class" simply defines the pressure rating at a particular temperature of the fitting, depending on the material. 150 lb fittings can be plated/dipped carbon steel (many different grades/alloys), unplated carbon steel, stainless steel(again many different grades/alloys), hastelloy etc. These fittings can be castings, forgings or simply machined from bar. I am trying to find the tolerance on the OD of a 150 lb coupling regardless of material. The coupling I am referring to in this forum is a 1/2" NPT half coupling machined from 316 S.S. bar.

RE: Coupling (half) O.D. Tolerance

AARCUDA, if possible identify whether it is made to any standard or specification which, I would guess, will give manufacturing tolerances.

If not, if it's just a thing you can buy, tolerances may be up to each manufacturer.

Regards,

Mike

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