Center drilling aluminium

Hi, I am planning on milling some aluminium and the parts need some drilled holes. My plan was to center drill the holes on the MPCNC and finish drilling them by hand, once I got the exact locations. I did a few tests with different plunging speeds and different rpm’s but the drill looked like it was always wandering a bit. Does anybody have any tips or tricks? I just want a little mark where I should drill. Below is a picture of the center drill I am using. The rpm’s I have tried run from 10.000 (lowest my spindle will go) to 25.000, and for the plunge rate 200 mm/min to 50 mm/min.
Center drill

Drill bits like to wander.

I got a little bit of wandering when I did my cribbage board the first time. When drilling holes like that with a drill press, you center punch the holes to keep the drill bit from wandering in that initial cut. With my cribbage board, I was doing the outlines with an engraving bit, and I found that I could engrave “center punches” with the engraving but 0.5mm deep. The engraving bit did not wander. I was then able to put a 1/8" drill bit into the 1/8" collet and drill my holes 12mm deep with no problems.

My first solution though was to do the holes in 2 passes. The first was a 0.5mm deep hole, and I let the tool dwell there for a second or two, then lifted it and drilled. Sometimes there would be a little bit of wander with the first hole, but it would re-center during that dwell time, and then be OK when it actually plunged in.

Okay, so did you engrave a small point or like a little cross you could later center punch?

Just a little point. A “drill” operation in Estlcam, at 0.5mm depth.

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Thank you, will try that later today