Accept or not?

[clun]

Background: A repair scheme was called from manual that the material use is a 0.063" thikness Al plate. Unfortunately only a 0.061" plate is on-hand.
Query: The mechanic refues to use it because its 0.002" thinner than RS quoted. But the pocurement staff said that all the wrought mat'l have a tolerance in thickness (+/- 0.00X&quotso it's acceptable for work.

Any comment!!

 

[SuperStress]

clun,

If you have the material certification that states that the material in question was procured as .063 sheet per the applicable spec., then the mechanic doesn't have a reason to object.

Standard tolerances on .063 sheet will vary from manufacturer to manufacturer, but I've seen .003" as a tolerance from some of them.

If the mechanic still resists, is it not possible to contact the engineer who designed the repair to approve the variance? If not, is there another engineer available to approve it?

SuperStress

 

[TVP]

The Aluminum Association Aluminum Standards and Data lists the following tolerances for sheet/plate used in aerospace applications:

0.047-0.063 inch thickness
+ 0.0020 inches for width up to 47.24 inches
+ 0.0030 inches for width up to 70.87 inches
+ 0.0035 inches for width up to 86.61 inches

ASTM and ANSI standards use the tolerances developed by the Aluminum Association.

 

[clun]

Thanks for all your comment.

SuperStress
I can't agree any more with you as someone to approve the variance. I thought it's the most appropriate way to solve the problem.
Meanwhile, if the mat'l was pocured as 0.061", what's up?

TVP
Would you mind show me the ASTM and ANSI standard no.?

 

[Miper]

My experience is that aluminum sheet bought by the pound is at the upper range of the tolerance, and aluminum sheet bought by the square foot is at the lower range of tolerance. Structural analysts should always consider both the low and high tolerances in their stress and stiffness calculations.

 

[SuperStress]

If the material was procured as .061" then it doesn't meet the drawing requirements and would need an approved engineering disposition to use it.

FYI, since .061" isn't a standard gage (that I'm aware of) it's pretty unlikely that the shop just has some lying around. It's almost certainly .063" stock on the low end of the tolerance range.

SuperStress

 

[TVP]

ASTM A 209 (metric counterpart is ASTM A 209M) and ANSI H35.2 (metric counterpart is ANSI H35.2M). You can obtain these standards from Global Engineering Documents using the following link:

http://www.global.ihs.com

 

[oiam]

you can discuss standards all you want,,, but the mechanic has his credentials on the line for the work.
he has the right to refuse,,, you can discuss it with the FAA ,but be prepared to write some reports