Thread Call-outs
Thread Call-outs
(OP)
I have a vendor requesting we take off the metric reference dims on our thread call-outs. I can't find the paragraph to cite the practice one way or the other. Our drawings are in INCHES, and everything gets a metric reference.
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RE: Thread Call-outs
--Scott
http://www.wertel.pro
RE: Thread Call-outs
.250[6.35] -20 UNC-2B
Our vendor wants .250-20 UNC-2B.
Sorry for the confusion.
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RE: Thread Call-outs
But to have a vendor ask for a drawing revision just to take them off?
RE: Thread Call-outs
It is not like you have .250 dimension, but rather the whole .250-20 designation calling for certain Major diameter, Minor diameter, Pitch diameter, Pitch. Why not convert pitch .250[6.35]-20[1.27]?
.250-20 UNC-2B looks perfectly fine even on full-metric drawing.
Does your vendor have authority to demand drawing to be revised? – That's another story.
But if I was him I would charge you extra for measuring the same major diameter with two different micrometers.
RE: Thread Call-outs
In fact I thought dual dimensioning (except on data sheets, interface drawings etc.) had come to be frowned on? Plus aren't ref dims usually in parenthesis not square brackets?
I certainly don't believe your current call out is supported by ASME Y14.6 which is I believe the relevant spec for thread call outs. Or in B1.1 which is the actual thread spec.
When you say 'paragraph' what spec are you looking in?
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RE: Thread Call-outs
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Thread Call-outs
"Art without engineering is dreaming; Engineering without art is calculating."
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RE: Thread Call-outs
Chris
SolidWorks 11
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SolidWorks Legion
RE: Thread Call-outs
RE: Thread Call-outs
From Machinery's Handbook:
Screw Thread Designation.—The basic method of designating a screw thread is used where the standard tolerances or limits of size based on the standard length of engagement are applicable. The designation specifies in sequence the nominal size, number of threads per inch, thread series symbol, thread class symbol, and the gaging system number per ASME/ANSI B1.3M. The nominal size is the basic major diameter and is specified as the fractional diameter, screw number, or their decimal equivalent. Where decimal equivalents are used for size callout, they shall be interpreted as being nominal size designations only and shall have no dimensional significance beyond the fractional size or number designation. The symbol LH is placed after the thread class symbol to indicate a left-hand thread:
Examples:
1⁄4–20 UNC-2A (21) or 0.250–20 UNC-2A (21)
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RE: Thread Call-outs
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Thread Call-outs
RE: Thread Call-outs
One more vote for your vendor. The machinist will never find a tap labeled 6.35-20UNC.
At least, I hope he won't.
RE: Thread Call-outs
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Thread Call-outs
I have gone the whole route on this during the last 25 years and we learned the hard way.
I have re-read MadMango's post and he should list his threads in inches - not converting inch thread dim's to metric.
RE: Thread Call-outs
In that case to my mind the significant thing becomes to not have screws of similar size in the different systems that could get mixed up.
On newer designs we're trying to go mostly metric for fasteners to help field service out when in other parts of the world.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Thread Call-outs
RE: Thread Call-outs
Matt Lorono, CSWP
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