Slotting Aluminum

See below- this is 6061 aluminum bar, 3/4" square & about 18" long. It has a 3/16" wide x 3/16" deep slot & I just slotted four of these using my go-to Amana HSS1621 (HSS single flute, 3/16"). Used .031" DOC, 21000RPM & just ran it right down the center of the slot six times. The first four passes went well but the fifth and sixth struggled. It ended up leaving chips glued to the side walls, and I assume this is due to rubbing & chips welding to the wall as it gets deeper and can’t clear chips properly.

I slotted something similar a few weeks ago using all the same settings, but the slot was 1/4" wide & I cut ‘around’ the inside perimeter of the slot. It cut beautifully.

Aluminum cutters - maybe I’m not describing it quite right, but do you think what I’m seeing is because I’m cutting a 3/16" slot with a 3/16" bit? How would you do this? I can change the slot width… maybe make it .200" wide & use the same bit, or I could switch to a smaller bit (or something better for this) & keep the slot width the same.

If (when) I work this out I’ll have an opportunity to cut lots of these.


What feed rate did you use?

If you’re not already using an air blast then that would be my first suggestion, and to add a mister would be the second. Air to evacuate the chips from the slot + mist to cool/lubricate :+1:

you could decrease the depth of cut but you may still get the same issue.


Make the slot wider or use a smaller bit so you’re pocketing and have a gap for chips.


You’re having chip clearing issues - a -strong- air blast and a little lubrication would help (I use alcohol, others use all sorts of stuff, soluble oils, kroil, wd-40…). You likely also have chips welded to the flutes of the tool (look at it under magnification…it’s a little like looking behind the dryer - always surprising)


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