10mm Aluminium Plate Not Flat

[gtrdude]

Hi, bit of a noob question here. I purchased a 200x300mm 10mm aluminium plate from my local metal supplier for the work surface on my PCB milling machine. They had to cut it from a large sheet with a saw. I expected this to be flat and the corners precise. Unfortunately, the plate was not anywhere near flat and the corners were terrible. Now I'm $70AUS out of pocket and I'm stuck with some useless aluminium.

Is it normal to have to get aluminium plate flattened? If so how is it usually done? Am I wasting my time and money? Should I look for another type of aluminium that is sold dead flat?

Massive frustration. So close to the finish line!! Please help me!

Paul

[Ken_Shea]

If it is plate then my experience is that it will be reasonably flat, having been cut from a chunk it would be understandable that it would need to be squared.

If it was cut from a extruded piece then that width approx 8" or 12" depending how it was cut would not be flat at all from my experience.

You could have that piece squared up and them surfaced on a mill, this should get it pretty square and flat no bigger then it is.
Unfortunately that will likely set you back another $30-$40.

They must have charged you a minimum charge at that price.

Are you in the USA?

[ger21]

Should I look for another type of aluminium that is sold dead flat?

mic6, or cast tooling plate

[Geof]

.....You could have that piece squared up and them surfaced on a mill, this should get it pretty square and flat no bigger then it is.

Unfortunately surfacing it may even make it worse. There is a lot of stress in the surface of both extruded material and rolled plate. When you take a cut off one surface the unbalanced stress then makes it warp. So you take a cut of the other side and it warps back - to far. So you take another cut. etc etc.

This is why cast tooling plate is made - no stresses.

[Ken_Shea]

Geof,
You are correct in theory, but that has not been in my semi-limited experience any real problem at all and I have done that to somewhat larger pieces then the 200x300mm that Paul is working with. It is thin and will also be bolted down, this should eliminate the small amount that it may bow or warp from the uneven stress.

Mic-6 is clearly the way to go but he did mention the infamous $$$$ so my reply was weighted toward that consideration.

[ViperTX]

Geesch......if you provide the vendor with a drawing indicating tolerances.....then you have a legitimate complaint if it's not to your drawing specifications.....if you just buy something then the vendor will tell you what their tolerances are......pretty basic stuff....

[widgitmaster]

This is why I use precision ground MIC-6 plates for all my serious projects!
Standard 6061 Mill Finish aluminum plate is NEVER flat, and cutting the skin off one side of a plate that thin will make it curl like a "Corn Chip"

If its any help, you can sell the bad piece of metal on eBay, and get most of your money back!
Then . . . .
Contact Speedy Metals on eBay 1-888-744-4140, speedymtls@aol.com

They have great prices, no minimum, free cutting, and ship world wide!

Good luck,
Eric

[Arthur Clampitt]

Being from Australia myself I can advise that asking for MIC6 or "Cast aluminium plate" here will get you a blank look and not much else !! It's hard enough to find a supplier that actually stocks anything thicker than 12mm (1/2") plate , let alone anything thicker or fancier in rhe way od alumininium ( aluminum to the US !!)

1" plate (25mm) is generally " special order" and you need to want a full length or complete sheet !

Au$70 does seem a little too much for that piece though , even if it were flat :-)

Art

[Arthur Clampitt]

rhe way od = the way of ( thick fingers :-) )

[ironDigit]

if its the worktable that you'll be bolting your work dwn too the corners shouldn't be a real practical problem for you

and if you got a flatplate like the granite ones and you really need too stikk to the budget i'ld try bolting it down and scraping it shouldn't be that hard on aluminum jusst bolt down very well not only the corners .If you got some slack in your budget i'll ad this plate to my stock and try and get meself some real flat piece by communicating with the seller

good lukk m8

[DareBee]

Depending on the type of metal vender you visited (and your knowledge of what you needed) there is a good chance you have purchased utility Aluminum (3003 series) and it will be useless as a machine table.
I will assume you are in Australia, otherwise you could drop my shop and I would sell some 1/2 Mic6 cheap (NOS).
Even Mic6 has a manufacturer spec tolerance of .005" flatness per foot; I have never seen any even half that bad but that is the spec.

[phantomcow2]

How bad is it? Bandsaw cut will not produce a really square piece, especially if its all cut from a larger sheet of it. Bandsaws are NOT accurate machines.
If you really need it flat and square, find somebody with a moderate sized mill, face and square it up.
Also, I doubt its useless aluminum, aluminum is never useless . I keep all my scraps for this reason