Repetitive Features
Repetitive Features
(OP)
I have seen one customers drawings come through with a call out like the following and it drives me nuts:
.138-32 UNC-2B
3X
To me it seems in order to comply with ANSI/ASME Y14.5M-1994 you should call out the above like this:
3X 6-32 UNC-2B
In section 1.9.5 (repetitive features or dimensions) it does not state where the "3X" has to be... but in sections 1.9.5.1 (series and patterns) and 1.9.5.2 (spacing) it states "...number of features and an X followed by the size dimension of the feature.)
So does this mean the first call out is okay?
Is calling the threads out by .138 even legal? I would think using the screw designator is the proper way (6-32) Who orders a .138-32 tap?
Thoughts? Does it really matter?





RE: Repetitive Features
If you bid the price up on the 'special order' tap, you may inspire a change, or someone more 'forgiving' might just bid using a 6-32 UNC-2B.
RE: Repetitive Features
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RE: Repetitive Features
I have seen drawings with all threads called out with the decimal shown. This is confusing. Calling out ".138-32 UNC-2B" vs "6-32 UNC-2B" can mistakenly give you a different tolerance.
Chris
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RE: Repetitive Features
RE: Repetitive Features
Is it grounds for rejecting the drawing? You were able to determine by looking at it how many there were altogether, yes?
As to the thread designation - it is not in ASME Y14.5M-1994's scope. The drawing states .138-32 UNC-2B and the Machinist Handbook gives the nominal dia of a 6 as .138
RE: Repetitive Features
I think this is pretty self explanatory. The dimension comes after the qty. Although it could be argued that because they use the word MAY, this is not so much a requirement as a suggestion. I don't think there is anything wrong with the thread callout, it may not be what I would prefer to see but the notes' form is otherwise correct.
David
RE: Repetitive Features
RE: Repetitive Features
Heckler![[americanflag] americanflag](https://www.tipmaster.com/images/americanflag.gif)
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
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This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.
RE: Repetitive Features
UN threads in the US are covered by ASME B1.1-2003. According to section 6 the way the thread is called out is perfectly legal to this standard.
Now the problem may be that most drawings in the US don’t actually reference B1.1 so almost no one actually knows what spec is controlling the threads and seem to rely on Machineries or similar
I just turned the page and 14.6 section 3.2.1.3 actually suggests that just the number size shouldn’t be shown, but if used should be followed by the decimal in parenthesis (we do this). This is a slight mis-match to B1.1 which seems to say you can just have the number. The copy of 14.6 I have is 2001 although 14.5M-1994 references the 1978 edition.
Either way though, the thread designation you have would appear to be legal assuming the drawing somehow references, directly or indirectly (e.g. by calling up 14.5 in the title block etc.), 14.6 or B1.1.
Now if these standards aren’t referenced in any way then arguably you can do what the heck you like, which is why I’m a stickler for somehow referencing any invoked standards.
KENAT, probably the least qualified checker you'll ever meet...
RE: Repetitive Features
KENAT, probably the least qualified checker you'll ever meet...
RE: Repetitive Features
Once again somebody has absconded with my Y14.5 copy. Does Y14.5 not still reference ASME B1.1 in its list of referenced documents?
If so, and if you explicitly reference Y14.5 on a drawing note, and then add a second note referencing ASME B1.1, should you put that 2nd note in parentheses (indicating it is a reference for reference only), since it's already referenced in the Y14.5 standard? :)
Seriously, as KENAT points out, if there is a discrepancy between nomenclature/callout form between the two standards, which one takes precedence? If you really are going to go down this specification and standardization route, and have multiple referenced standards/specs on your drawings, you need to include a note regarding OOP. Been there, seen a company tied up in knots by a nasty government-paid QC type, bought a ticket out.
RE: Repetitive Features
14.6 isn't particulary well worded on the issue:
The first paragraph implies you can have just the screw number while the second says you shouldn't, maybe it's just clarifying what the first paragraph said but I'm starting to lose track of my thoughts.
However for the OP, regardless of which standard, the designation was correct.
btrue, in your case I belive the problem was the QC guy more than the standards.
KENAT, probably the least qualified checker you'll ever meet...
RE: Repetitive Features
In my experience with working defense/military contracts if it's spelled out in the requirements document or unless you have taken exception to it in the complience matrix then you're on the hook.
Heckler![[americanflag] americanflag](https://www.tipmaster.com/images/americanflag.gif)
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
o
_`\(,_
(_)/ (_)
This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.