Drilling aluminum plate causing bubbles on backside

[TheHiggsBroson]

Anyone ever experienced this when drilling through aluminum?



This is on the backside. Been running at 5200 RPM, 1/8" thick, rapid out drilling with a 1/4" tool. Don't use any coolant (doing this on a cnc router) but I do have air blast on it. I managed to make a few good pieces but just broke a bit as the plate began to flex as the bubbles pushed on the my mdf board below. Could be a clamping issue, I am clamping on the corners and I definitely notice the plate flexing up and down as it drills. Or maybe peck drilling would help.

Bit isn't anything special (something from home depot I believe), but I had opened it new and ran 2 plates with it before this started happening.

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[InMesh]

I would say speed too fast and no coolant would be the culprit otherwise blunt cutter.

[TheHiggsBroson]

I would say speed too fast and no coolant would be the culprit otherwise blunt cutter.

I found a HSS drill that is working much better now, cut a few plates already. Clamping down a little differently and apply a thin coat of cutting lube prior to every part, seems to halve solved the issue so far.

[InMesh]

Splendid Some times it's easier to use a drill because you have a finer point to start the cut with a slot mill the two cutting sides of the cutting head are level and trying to cut at the same time that can make down cutting a hole difficult ,I have just picked up things over many years .