Milling a plate of Al., larger than mill table

T

timbertoes

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Howdy, I guess we all have to face this situation once in a while.
(Picture at bottom)
Particulars:
its a rifle rest base.
1" thick, 12" square Aluminum.

Mill table is 8 deep. (PM45)
Cutter: Glacern 45 face Mill. (new, and OMG I love it)

Desired outcome: visually appealing, and as best as possible flatness. whatever that really is.

So far: Moving clamps, and moving the piece, can mill the whole piece.

I understand the problem of moving a piece thats not really flat on the bottom, and also we have different clamping places. its a tough call in any event.

** having said all that, would love to hear of best case solutions, to just the above.

Now on to the second "thing".....

one surface is done. pretty good considering I think. But It needs hand-flat. I think. hehe.
Is this where I should be asking:
what drill mounted "wheels" would be usefull for taking just a little at a time, to blend in the few ridges here and there. they are a few thosuandths.

And in general, what drill mounted wheels woudl be usefull for starting, or finishing, a polishing of the Aluminum.

I say Drill-mounted, becuase....well, it seems with a 12" square its a bit much to present to a buffer setup ???

sorry lots of questions :)

here is a pic, if it helps. you can see I do have a gray Norton de-burring wheel. I am not adverse to files. you can see I started a little filing. but stopped, cause I might ruin it. lol.



12sqalplate1-M.jpg

- - - Updated - - -

of interesting note;
that starret rule (24") reads "flat and true" in the direction of the milling, and in the other direction, reads a high spot approx in the center.

12sqalplate1-M.jpg
 
I was kinda thinking about a sander as well.


One thing, I am getting a bit ahead of myself... it will get cut and edge milled to a mostly triangle shape. so some of the flatness issue cures itself.
a feeler guage measurment showed .01 to .012 under the steel rule at a far edge.

I think I should proceed with it, but with this one somewhat reasonable face, go ahead and start trying some edge squaring, layout/bandsawing and milling to the triangle shape. need to find some hole locations from reference edges as well.
better put steps on paper and think them through. :)
 
Yes I would draw it out on paper first. Mabe a T insted of a triangle. That would leave some good stock left over.
 
Make you a fly cutter for your mill and take a skim cut on it. Being its Alum it will work ok fly cutting it.
 
If you have a large enough flat surface you can glue some emery paper down and hand lap it using finer grades as you go. Once everything is blended you can buff it. The high gloss will look great except on sunny days when it blinds you. You might want to think about bead blasting.
 
pineyfolks said:
If you have a large enough flat surface you can glue some emery paper down and hand lap it using finer grades as you go. Once everything is blended you can buff it. The high gloss will look great except on sunny days when it blinds you. You might want to think about bead blasting.
Click to expand...

ah, yes. the table saw surface....but that would mean cleaning it up, from a storage bench back to a clean table saw. lol.
 
timbertoes said:
and as best as possible flatness. whatever that really is.

So far: Moving clamps, and moving the piece, can mill the whole piece.

I understand the problem of moving a piece thats not really flat on the bottom, and also we have different clamping places. its a tough call in any event.

** having said all that, would love to hear of best case solutions, to just the above.

Now on to the second "thing".....

one surface is done. pretty good considering I think. But It needs hand-flat.
Click to expand...

If the "done" surface is flat (.001-.002 TIR) and with a decent finish - preferably better than a 63RMS the following should work.

Clean up the mill table surface, E.G.: stone it flat, clean it with acetone.
Get yourself some double sided carpet tape. put the tape on the clean mill table.
Clean the good side of the material like you did with the mill table. peel the paper off the tape and locate the clean side of the mat'l on the carpet tape being careful to position it where you can get most access at once.
Take VERY light cuts till clean. Remove the part, repeat the cleaning procedures again and move the part to access the rest of it.

This should make the part flat and parallel to the already finished side.
Couple of tips: make sure the spindle is square to the machine table and don't run the cutter where there is no support underneath.
I can't emphasize enough the cleaning part of this. It is imperative to the gripping ability of the tape. If done right you will be amazed at how difficult it will be to remove the part and the tape.

One question: what is "hand flat"?

HTH
Benz
 
perhaps a different order of operations. Cut it close to finished triangle shape and turn the long flat side to the back of the table towards the column. Maybe leave some tabs for clamping that wont get machined. Would that not shrink down the 12" dimension? Use that flycutter at this point. Just a thought. Hard to see it with out seeing it or being familiar to your machine. Also, if you lap the one side flat, you should be able to machine the other side in two steps as you will have a flat surface you will be machining parallel to. That should help minimize error from setting up twice.
 
yes..on getting it to the triangle shape before milling the next surface. It will help.
And yes on that carpet tape......lord knows that is easy to forget about. and its darn hard to get things off of it too.

Btw, I am using a Glacern 45 facemill cutter that arrived a few days ago. It is really,really nice.

how nice....you asked ? :)

its like this....had set it up for a measly .01-ish" cut.....and I did not think I had setup the depth at all....until i saw the chips begin and the new shiny mirror surface it left behind.
Mill acted like it was not even cutting, so smooth and easy. "like Butter" :)
 
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