Sheet stock tolerances
Sheet stock tolerances
(OP)
Have a requirement for .105 steel stock on a drawing. The question has come up about whether the normal drawing tolerance applies to this (+/- .010 for example) or does the ASTM requirement for sheet tolerancing (in this case ASTM-A568, +.006/- .000) apply? And should the ASTM tolerance be put on the drawing?





RE: Sheet stock tolerances
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sheet stock tolerances
RE: Sheet stock tolerances
If the drawing says 'STOCK' or 'STK' then you have to reference the relevant material spec (ASTM-A568 in your case) for actual tolerances - general drawing 'block' tolerances do not apply. You wouldn't normally copy the tolerances from the standard onto the drawing.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sheet stock tolerances
Be careful. Aerospace wrought materials [like sheet, plates, extrusions, etc] have specs that control tolerances for each form AND alloy type [aluminum, steel, CRES, titanium, etc].
ASTM materials are a much different animal. What bothers me is the thickness You indicated: 0.105-inch... which is a highly non-standard. In this case there would have to be a unique purchase agreement [contract] in-place that specifies sheet thickness, width and length tolerances.
Regards, Wil Taylor
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RE: Sheet stock tolerances
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RE: Sheet stock tolerances
RE: Sheet stock tolerances
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Greg Locock
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RE: Sheet stock tolerances
we'll often refer to 0.1" thk Al sheet, which might be referred to in the materials world (as it truly might be) as 12swg. i guess the inherent advantage to this is buying 12 swg thick sheet satisfies the drwg call-out (for 0.1" thk).
in any case, i don't think standard drwg tolerances (+-0.010) apply to thickness of stock sheets.
i thnk another clarification comes from how the sheet is annotated in the BoM. if the engineer wanted a non-standard thickness then the detail view would show the finished thickness (say 0.115") as a hard dim'n, and the BoM would call out "0.125" thick"
Quando Omni Flunkus Moritati
RE: Sheet stock tolerances
According to 'Y14.5 the tolerances on stock material is that given by the stock material specification. Unless there is a note to override this, that is what would generally be used.
The ugly part is that the tolerance given in material specifications varies depending on the width the material is originally rolled to. It is a spec that tells what the buyer of material direct from the rolling mill can expect. After the material is cut to smaller sizes, it isn't easy to tell what the original width was. Side-by-side one can have pieces where one would have failed the thickness tolerance of the other.
If it is important, I'd create or look for an in-house material spec that is used to constrain material to a more desirable range.