Calculation diameter beginning for NPT thread.
Calculation diameter beginning for NPT thread.
(OP)
Hi,Can anybody know how to calculate this,the diameter beginning for 3/4-14 NPT (for box & pin thread),Thanks for any helping.
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Calculation diameter beginning for NPT thread.
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RE: Calculation diameter beginning for NPT thread.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Calculation diameter beginning for NPT thread.
http://thread-chart.ueuo.com/NPT-Thread-Specificat...
RE: Calculation diameter beginning for NPT thread.
By definition, the two NPT threads making up the "threaded joint" WILL interfere with each other, and so CANNOT be represented by your diagram. (Now, if you "drew" the bottom of the threads in both sides, then "slid" the two together until the threads overlapped, you'd start to see the effect of threading the two.)
BUT - each tapered NPT type joint will vary depending on tolerances of the threads and amount of deformation when they are screwed together.
RE: Calculation diameter beginning for NPT thread.
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Calculation diameter beginning for NPT thread.
RE: Calculation diameter beginning for NPT thread.
What buddy is after is the ingress point for roughing operation on the Box minor diameter.
Regards,
Cockroach
RE: Calculation diameter beginning for NPT thread.
RE: Calculation diameter beginning for NPT thread.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Calculation diameter beginning for NPT thread.
The angle is 1.78333333 degrees
Calculate the "opposite" length, using that basic trig formula TOA
The opposite length is subtracted from the outside diameter of a 3/4-inch NPT.
the OD of a 3/4 NPT is 1.050
1.050-[Tan 1.78333333 (.546)]2 = 1.016 diameter
That's the small diameter on the pin
Of course, the opening for the 3/4-NPT is 1.050; which is the nominal size of 3/4-inch pipe. (your left hand view)
All assuming, of course, you are only using the effective thread length.
For lack of any other explanation I can give.
Charlie
www.facsco.com
RE: Calculation diameter beginning for NPT thread.
That is, don't try to "calculate" some arbitrary hole dia based on assumed thread pitches, thread engagements, and tapered hole diamter. Just look it up:
Standard NPT Tap Drill Sizes
NPT Size
Tap Drill Size (in.)
Decimal Equivalent (in.)
1/16 - 27
"C"
0.242
========
1/8 - 27
"Q"
0.332
========
1/4 - 18
7/16
0.438
========
3/8 - 18
9/16
0.562
========
1/2 - 14
45/64
0.703
========
3/4 - 14
29/32
0.906
=========
1.0 - 11•1/2
1•9/64
1.141
=========
1•1/4 - 11•1/2
1•31/64
1.484
=========
1•1/2 - 11•1/2
1•23/32
1.719
=========
2.0 - 11•1/2
2•3/16
2.188
=========
2•1/2 - 8
2•39/64
2.609
=========
3.0 - 8
3•15/64
3.234
Ref: http://www.engineershandbook.com/Tables/npttap.htm