Machine shop responsibility to comply with "Industry Standard". 7

[powerhound]

I'd like to get everyones take on an issue. If a machine shop gets a print with no GD&T on it as well as no reference to any dimensioning standard, how much responsibility does a machine shop have to catch any unspecified tolerances. For example: a 3 foot long rail with various slots and holes along the length has about .020" of bow in it. Is this something a machinist should have made a special effort to avoid in the absence of any other information or should this part be considered "to print" and called good?

The kickback I'm getting from the customer is that "Industry Standard" dictates that that straightness tolerance should be the same as the tightest tolerance in the default tolerance block. I've heard this before but I thought in modern times, industry standard had fallen by the wayside since it's not documented or enforceable.

Looking forward to the feedback...

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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[MechNorth]

I have seen "workmanship" notes, but they harken back to the days of master machinists / master moldmakers, when they were still rather commonplace, and there was a certain quality that implicitly came with their skills. In today's world, it's meaningless.

Jim Sykes, P.Eng, GDTP-S
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[ajack1]

The one “industry standard” that springs to mind but is seldom if ever seen on drawings is all sizes should be correct at 20 degrees C.

Is that taken as a given or could someone legitimately argue that the part is not undersize it is just not hot enough?

 

[powerhound]

That is actually in the GD&T standard. Invoking the standard on the print definitively invokes that fundamental rule. This one can be backed up.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[drawoh]

Toddr8541,

I send a PO to Billy Bob and Cousin Elmo's machine shop. I want my part number 123-456 fabricated as per my drawing, coincidentally named 123-456. My drawing states that my dimensions and tolerances are to be interepreted to ASME Y14.5M-1982.

What does this mean?

[ol]
[li]My PO is equivalent to a contract.[/li]
[li]The PO calls up my drawing 123-456, so my drawing is part of a contract.[/li]
[li]My drawing calls up ASME Y14.5M-1982, so the ASME standard is part of the contract.[/li]
[/ol]

A note on my drawing stating that the work "must meet quality workmenship standards" has no meaning unless the standard is explicitly identified. Perhaps it is my in-house standard, in which case, I have to pass a copy on to Billy Bob and Cousin Elmo, and perhaps, provide training in it.

This is a big picture issue. So many people out there have a "generate drawing" process. They do not understand or care that someone out there has to order parts from the drawing, and write a meaningfuly PO. Several others, including your inspector, have to read the drawing and interpret it correctly and consistently.

JHG