what controls concentricty when no callout? 1

[ronj100]

I have a hamilton sundstand drawing with several diameters along an axis. The diameters only have feature of size tolerance.
No concentricity is listed for the multiple diameters. How is concentricity infered or controlled on such a drawing? What is the Y14.5 spec that can be used to answwr this question?
(the print states that it is to be interpreted by DOD-STD-100C, that spec points to Y14.5M)

 

[MintJulep]

what controls concentricty when no callout? Luck.

 

[ctopher]

I agree with NJ, luck.
It's a lazy way, just call out a spec and cross your fingers they line up.

Chris, CSWA
SolidWorks 13
ctopher's home
SolidWorks Legion

 

[dgallup]

Does it need to be controlled? Evidently not according to the drawing.

----------------------------------------

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.

 

[Timelord]

The manufacturing process controls the concentricity. They have probable assumed the diameters will all be cut on the same setup/axis, perhaps because they were in the past. No excuse though, very poor drawing.

Timelord

 

[MikeHalloran]

Implied concentricity is the sort of thing that used to be controlled by a company's own internal manufacturing standards, when it could reasonably be assumed that your own machinists would be making your parts, using the same process that everyone understood, and they could and would just walk over to an engineer's desk with a question.
The standard answer to the particular question is "dead nuts/ same setup".

Things change.




Mike Halloran
Pembroke Pines, FL, USA

 

[Belanger]

Just to rehash what the others are saying... If there is no title block note about this, or a company spec referenced to address the coaxiality, then the drawing is just plain ambiguous. Perfectly fine to ask your customer what they really want, since they chose to release a confusing print.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

DOD-STD-100 was replaced a long time ago by MIL-STD-100, which was cancelled in 2001. The C version is from 1978 and doesn't appear to be available from the Defense Logistics Agency (DLA). DOD-STD-100C predates the 1982 version of Y14.5. Unless the drawing says otherwise, you need to look at the 1973 version of the 'Y14.5 standard, which won't help you because it also says nothing about implied concentricity.

If this is a build-to-print contract, mention this problem to your legal department so that no one using this product can come after you/your company for making one that has faulty performance or so there is a defense in place under an as-is type of sale.

In similar situations, it is possible to make some money by generating an engineering development contract to determine such missing information. It could be based on engineering analysis, product testing, or inspection of similar parts for existing acceptable variations. Often an entire drawing package will be similarly defective, with references to difficult to obtain specifications, missing dimensions, missing tolerances, and unobtainable materials or processes.

 

[fsincox]

This is so common with our drawings and I suspected it would be with their's too. My wife is an engineer for them, I work for an aviation competetor. I wish I could say it is not true with our newer drawings, but, If I do not do it myslef it will be. The "word" is not getting out very well IMHO. I suspected it is true of them too. The good "old boy" network strikes again.
Frank