No description - thickness tolerance

[Kiomtu]

Dears,
no info about thickness tolerance on B168, thk 4mm and width over 1600mm, hot rolled sheet condition.
how can I find the tolerance? and is it ok to use internal tolerance in that case? somewhere described on ASTM book like "ok to use internal spec"? also, any definitions on ASTM that if plus and minus are +0.5,-0.5mm stated on ASTM, and then if requirement is plus 0mm, does it make sense to shift minus side only, which +0,-1.0mm? any description on ASTM book?

Thank you in advance,
Kiomtu

 

[gr2vessels]

I suggest Kiomtu, read the ASTM B168 standard, you will find in the standard all answers to your questions. The thickness tolerance mentioned in the standard is precisely what they wrote;- plus minus the value stated in Table 7.
However, the standard does not have provision for 4 mm thick sheet with width above 1520 mm, hence your sheet width over 1600 mm might not be a standard material and therefore the standard tolerances do not apply. If they do, the tolerance is + 0.41 / - 0.41 mm. It cannot be shifted to all positive or all negative tolerance, because it won't be certified for compliance with ASTM B168.
Cheers,
gr2vessels

 

[Kiomtu]

Dear gr2vessels,
appreciate your comment. then if the standard tolerances do not apply what is the one of the solutions? is it ok to use internal thickness tolerances? found any official comment from ASTM?

 

[gr2vessels]

Sorry Kiomtu,
I'm not very familiar with the term 'internal tolerance'. Can you please clarify?
I'm also having trouble with associating the non-standard size sheet with the ASTM B168 you mention. The size of this sheet metal should not exceed the standard size of 1520 mm. In that case, the thickness tolerance should be in accordance with ASTM B168, Table 7.
However, if you insist the sheet size does not conform to ASTM B168, then the claim the sheet metal has been manufactured to ASTM B168 is incorrect. Perhaps the composition is also different, perhaps the certificate is not quite believable and so on. In that case, you need to do extensive thickness measurements of the sheet metal to establish the actual thickness and forget the tolerance. Perhaps a test of the chemical composition will help. Sorry, I was unable to locate any official communication from ASTM on the above topic.
Best regards,
gr2vessels