View Single Post
  #5   Report Post  
Posted to rec.crafts.metalworking
Bob La Londe[_7_] Bob La Londe[_7_] is offline
external usenet poster
 
Posts: 1,768
Default 6061-T6511 - Dimensional and Flatness Tolerance

On 2/21/2021 3:13 PM, Carl wrote:
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.
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.Â* No mention of flatness, just "all other tolerances ASTM B221".


I always forget McMaster Carr for stuff like that. They are a great
information resource.



--
This email has been checked for viruses by AVG.
https://www.avg.com