On 2/21/21 1:11 PM, Bob La Londe wrote:
I've bought 6061 T6511 from several vendors.Â* Is there a spec I can look
up for what what should be considered acceptable?

1.Â* One consistently provides out of flat stock. Sometimes more than
.015 across a piece of 1/2x6 flat bar.Â* (ACROSS)

2.Â* One has certain sizes that are from 0.003 to 0.050+ over size, but
mixed.Â* Some a little over.Â* Some a lot over.Â* I can't grab two bars and
cut them to length and use them together even for rough work unless I
also size them on all dimensions.

3.Â* Another sent me some stock that is from .005 to .01 under size on
all dimensions.

I mentioned the problem to number 1 and they said its within spec and
sent me a spec number.Â* That was a long time ago, and it was easier to
just stop buying from them at the time.Â* Other vendors did not provide
stock in the same sizes warped to the same degree.

I also asked about the huge stock size variance from number 2, and they
said I should just machine it to size.Â* They are partially right, but I
due a fair amount of work that doesn't need all six sides machined if
the stock is nominally close to the same size.Â* I didn't quit buying
from, but I don't buy much from them due to price.Â* Also instead of
stocking or bringing in a requested size stock for me they want me to
buy larger more expensive stock and just machine off and throw away the
rest.Â* "Bring in the right size stock?Â* No just buy bigger and throw
away 25% of it."

I have not said anything to number 3, but I recently tried to run some
stock in a pre-made fixture plates and found myself having to add shims
to my edge clamps to hold the stock.Â* They are an order of magnitude
better price than number 1 or 2 and have the best overall selection. All
of the stock I have gotten from them has decent flatness.Â* I still would
like to continue buying stock from them on a regular basis, but I'd like
to know what the spec is for 6061-T6511 acceptable dimensional accuracy
before I say anything.Â* O/+ seems like it would be acceptable, but (-) I
would not think should be at all.Â* Its shaving pennies off value to
increase profits.



Just as one comparison point McMaster Carr shows a thickness tolerance
of +/- 0.009" for 1/2" x 6" x length extruded 6061-T6511 in both sheets
and bars. No mention of flatness, just "all other tolerances ASTM B221".

--
Regards,
Carl