Clamping Aluminium Plate

[bob12345]

Hi all, I need to clamp an 8mm x 250mm square piece of cast aluminium plate to machine a small number of 3mm holes with 6mm counterbores.

The already machined surface of piece needs to be protected at all costs as it will become the print bed of a fairly high end (in home user standards) 3d printer.

I only have the common milling machine hold down clamps that are sold everywhere and not much else, so was wondering what the advice was to securely hold the workpiece without marking the surface or distorting the piece in any way.

I know my usual "tighten the clamps down with the force of a thousand sun's" is out, so was thinking of raising the whole thing off the table with 1x2x3 blocks to get the clearance to drill the through holes and place a piece of Alu beer can shim over the blocks, then use a few bits of sacrifical aluminium plate under the step clamps to spread the force out, does that sound reasonable?

 

[Asm109]

Use paint stir sticks to spread load and prevent scratching.
Place part on sacrificial piece of MDF (aka high quality particle board)

 

[bob12345]

Use paint stir sticks to spread load and prevent scratching.
Place part on sacrificial piece of MDF (aka high quality particle board)

Thanks, that sounds like a plan, i'll grab some stir sticks tomorrow and give that a try.

 

[markba633csi]

Yes, fastening the piece between wood substrates would prevent scratches and marks and would help prevent the piece from
moving around
For extra protection you could apply some peel-and-stick material such as shelf paper or plastic window covering

 

[Firstram]

If the holes in the aluminum are around the perimeter, drill a couple of 1/2" holes through the MDF where the center of your plate will land. Glue the plate down with contact cement or a healthy coat of spray adhesive, always coat both surfaces! You can also block it in place with wood strips for a little extra insurance, clamp the MDF down and drill your holes. When you're finished, just flip it over and pour Lacquer thinner into the 1/2" holes to dissolve the glue. You can't warp or scratch the part if there are no clamps on the part!

 

[ChazzC]

I was thinking clamp the plate between two sheets of MDF: that will fully support & protect both sides, and prevent scratching the top surface with chips during the drilling process.

 

[bob12345]

Yes, fastening the piece between wood substrates would prevent scratches and marks and would help prevent the piece from
moving around
For extra protection you could apply some peel-and-stick material such as shelf paper or plastic window covering

Luckily the part still has the plastic film on both sides, I resisted the urge to peel it off.

 

[bob12345]

I was thinking clamp the plate between two sheets of MDF: that will fully support & protect both sides, and prevent scratching the top surface with chips during the drilling process.

That is a pretty good idea, if I can find some scraps i will give that a try, thanks.

 

[ChazzC]

That is a pretty good idea, if I can find some scraps i will give that a try, thanks.

I get a 2’ x 2’ or 2’ x 4’ “Project Panel” and have it cut to easier to handle sizes for my 5-1/2” circular saw. 1/2” & 1/4” thick.

 

[twhite]

Some good double sided tape to fasten down on a nice flat piece of material. Preferably a piece of aluminum. You will be shocked as to how well that holds. I have used this untold times. Simple and fast.


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