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Material strength

Material strength

Material strength

I have a small "L" bracket made from 2024-T3 QQ-A-250/5 at .13 thick each leg. The drawing calls out 2024-T351 QQ-A-200/3 in the latest revision. Is there much difference between the strengths of the 2 materials? All the other dim's are the same. What do you think?

RE: Material strength

It's not just the material itself, it's also what's implied by the AMS-QQ-A specification.

QQ-A-250/5 - Clad sheet and plate
QQ-A-200/3 - Extruded bar, rod, and shapes

Not the same animal.
If the clip is supposed to be made from an extruded angle, then it can be 200/3. That would be a cut-to-length & deburr before drilling fabrication process.
If instead the clip should be made from sheet, then it has to be bent first. Consider the miniumum bend radius of a 0.13 thick SHEET... Wow, that's at least 0.38".

I'm pretty sure you should do this with an extrusion. The drawing is probably correct. Why would you try to make this bracket by bending sheet?


RE: Material strength

That's perfect SparWeb. Thank you for your time and expertize.

RE: Material strength

is it a s/m clip or a machined/extrusion ?

Could it have been machined from a thick plate ? which would be very significant if it was meant to be an extrusion. I would expect an extrusion would have a much smaller bend rad than a s/m part (possibly not if the s/m was formed on O or W condition and heat treated.

in any case the part is not to B/P so it needs an engineering buy-off.

another day in paradise, or is paradise one day closer ?

RE: Material strength

Seems like a copy-paste error. Any number of times people making drawings will key in on the alloy and copy a similar note without paying much attention to the spec. It's just a spec, right? Then it goes for quotes and suppliers come back and ask for an adjustment, maybe, or it gets caught at first article when the certs come in, sometimes. Eventually someone notices and then there's a general panic and looking to see what the parts were actually made with, followed by lots of meetings, e-mails, and finally complaints about the number of changes the engineers generate, which results in cutting the drawing check budget some more. Sigh.

My favorite -not- was an aluminum tube bent into a shape like an unused staple. The making company charged a huge amount because it was called out 6061-T6, but the bend radius was a bit too small. They bought T6, annealed it, formed it, and then re-heat treated back to -T6. The tubing was just a grab handle for a box; the radius didn't matter much. But at least we got rid of sensible checkers.

RE: Material strength

daxmann... Sparweb's comments are dead-on.

What seems to be missing from Your side is an extruded profile number, such as: AND10134-xxxx, 'corporate profile #', etc.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

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