Richard,

I assume the block is to be machined completely through. If it is I would advise drilling through holes to take out most of the material. The drilled holes will also act as drain holes for coolant and allow cuttings to clear, which is essential for aluminium to avoid cuttings building up on the cutter which will result in the cutter snapping. Take cuts of about 1/8"- 3/16" max with as high a speed as you have. Listen out for any signs of chatter in the form of a high pitched screaming noise and reduce the feed/RPM to get the optimum rates.

Good luck.

Edited By Bob Rodgerson on 03/04/2018 11:16:44

I'd stitch drill it out with a 1/4" split point stub drill then clean up the faces with a 10mm ali specific cutter full 1/2" deep cuts going in 0.040" (1mm) at a time. 1200-1500rpm and a splash of paraffin. Stitch it right and there is no need to saw, just knocks out and 3 passes will have the job cleaned up to finished size.

This one is 15mm thick done as above though I used a smaller cutter as I wanted a smaller fillet in the corners.

Edited By JasonB on 03/04/2018 12:44:28

Edited By JasonB on 03/04/2018 13:18:21

+1 with Bob Rodgerson from me about making a hole right through early on in the procedure, as this lets you rinse the swarf out of the way. Cutting and re-cutting the loose material slows you down at best, and snaps the cutter only too easily. So you really need enough coolant to wash the cutter area clean, not just to lubricate the cutting edge. This is the one situation where the mess and commotion of flood coolant is worthwhile. All the calculations and rules of thumb for tooth load and cutter speed go out of the window if the cutter load is mostly recutting what it has already loosened. So it is worth cutting a hole right through the work piece, and washing the chips/swarf away so gravity is your friend.

Failing that you can achieve much the same result by blowing compressed air at the cutter to carry the swarf out of the immediate work area. This potentially makes even more mess than flood coolant!

Be very careful to protect your eyes before blowing compressed air onto swarf chips.

HTH Simon

A drill is the fastest way to clear material. Chain drilling is one alternative. Another way is to take out the bulk of the material using a series of holes with the largest drill that is feasible. Then make a series of plunge cuts with a fairly large end mill to clear away the material between the drilled holes. After that you can finish with your smaller end mill. You can cut aluminum at 500 to 600 ft/min using HSS tools. With carbide you can easily run 5 to 6 times the speed for HSS. The maximum speed available on your mill may limit you to lower cutting speeds. Kerosene or WD40 are popular lubricants when cutting aluminum. I prefer a mist of soluble oil. The mist helps blow out chips that otherwise might be recut.