Drilling clean holes in sheet aluminum?

In .050 metal a standard drill will not work well.
The point and angel of the drill will come out of the bottom of the piece before the drill sides will get into the piece.
This will cause the drill to wobble out the hole.
A flat bottom drill will wander around off location.
Center drill .050 metal will not help with a drill.

Use a end mill with center cut and a piece of wood hitting the bottom under it.
The wood does not have to be held tight in the vice just tight against the bottom of the piece.

Step drill do not always leave a round hole.
The will usually leave a burr on the exit side of the work piece.
 
General sheet metal trick, put a rag down first, then drill through the rag. Eliminates triangular holes and most of the tear out on the back side.
 
For 1/4 inch holes use a center drill with 1/4 pilot and if possible place wood under work.

C-clamps will hold wood and on first hole pressure will keep sheet against wood but apply top pressure on material and ease up as it goes through.

Then wood screw tgrougg hole with washer to attach to wood to keep tight to material.

Use step drill in hand drill at SLOW speed to clean up burs.

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How close are you to the edge of the aluminum? I work with a lot of sheet metal and usually punch my holes with a Roper Whitney No. 5 Junior or a RW #218 4-ton press. Don't have a RW No. 5 in front of me, so guessing you can go about 1 1/2" in from the edge. My #218 has a 12" throat. A used No. 5 is usually under $50 off eBay. They'll do a 1/4" hole in 16-gauge steel, wouldn't even work up a sweat through 0.050" aluminum.

Bruce
 
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