Sorry for the long read, I tried to anticipate questions and get you the info that I have found works for me and my setup.
I have tried many different things and have come to the conclusion that by keeping the machine within it’s limits in regards to feeds and speeds, lubrications is not nearly as critical as chip removal. If you can keep a clean path for the bit then it will cut very well without lubrication.
I have been pocketing 1 inch 6061 aluminum 7/8 inch deep using a 1/4 inch bit designed for aluminum.
My Setup:
I have two air hoses (details below) that pass through the dust shoe on opposite sides which keep a constant flow of air going to the bit. I don’t use a air diverter for the Dewalt. I want all the air possible to keep the aluminum chips flying rather than settling in the tool path. Keeping them airborne allows the vacuum attached to the dust shoe to suck them out and keep them out of the way. All that airflow also helps cool the bit and material.The only issue I am experiencing is trying to get my bit perfectly aligned vertically. Without a perfect vertical alignment of the bit I have experienced an uneven cut at the bottom of the pocket and rubbing near the top of the pocket which creates heat buildup and poor cut quality. This generally only happens from about .7 inches down to the 7/8 inch finish pass.
Depth of cut is .011 inches, Feed rate of 100 inches per minute with a 40% step over, and Dewalt setting of about 2 on the speed control dial.
This may sound like crazy fast speed at 100 ipm but slow cuts generate more heat and that is not good. Keeping the depth of cut shallow helps to prevent heat build up and does not stress the machine at all. The Dewalt doesn’t strain at all either.
To cut my part free from a long stick of aluminum, I create another pocket that is .33 inches tall extends a little past each side to keep a square end. This allows room for the bit to cut only one side at a time for 1/2 of the passes reducing stress on the machine and heat build up.
For airlines passing through the dust shoe I picked up some aquarium air hose. Added a T fitting to feed two air lines at once and a adapter to connect it to my air compressor, I inserted a piece of bailing wire inside the tubing so I could bend it to get it in the proper position and get the air to go right to the tip of the bit. I only push around 15 psi through the air hoses. This provides cooling and chip removal very effectively.
Another reason I don’t like liquid cooling/lubrications is that to be effective you need to use flood lubrication, not a drop here ant there. By just adding a little at a time, your aluminum chips will get suspended in the oil/lubricant which prevents evacuating them from the tool path. Re-cutting aluminum chips is never good.
Hope this gives you some ideas on how to proceed.
Charley