gglines wrote:

I'll be cutting pockets in 6061 aluminum and want to mill the bottoms as
smoothly as possible to cut down on finishing steps. Any recommended end
mills? The pockets will be 1" wide by 8" long by 1/4" deep.


The size of the end mill is limited by the corner radius of your pockets.
But, you want to use the largest end mill you can, as it will be stiffer
than a thin one. The smaller end mills deflect more when cutting, and
the tip of the flutes leave gouges in the bottom. A stub end mill is
stiffer than a regular length of cut version. Since your pocket is only
1/4" deep, that may help. 4-flute end mills are a little stiffer than
2-flute. Solid carbide end mills are astoundingly stiffer than HSS.

Coolant may be a big help. When doing a lot of metal removal in
a small area, the workpiece heats up, and aluminum will make a big
mess all over the cutter if it gets too hot.

If you want a very smooth bottom with minimal tracks on it, you will
need a VERY tight machine. Finishing the entire pocket to full dimensions
except leaving a little material (.005 - .010") on the bottom, and then
making a finishing pass to remove that last bit of metal may be needed
to reduce the visible tracks.

Jon