So I've been drilling standard 1/4" aluminium in a small (250W) consumer drill press. I've used a little oil to help, but I'm not sure if I'm doing it right. The holes seem okay though. They're 10mm diameter.

Judging by the swarf coming off the bit, am I doing it right or is there room for improvement? The edges of the swarf seem 'ripped' with little tags visible. And one side is dull, the other polished.


  • $\begingroup$ I suspect your parameters are all very good. Free machining steels contain sulfur or lead to make brittle spots to break machining swarf Likewise, cast iron has graphite flakes that break chips. I don't believe aluminum alloys have a chip breaking additive. Second point, I have seen many professional machine shops develop long swarf when cutting NON- free machining steels , so it is a good thing. $\endgroup$ – blacksmith37 Sep 7 at 23:54

Looks just fine. Aluminum can do that.

Long, stringy swarf(chips) is usually less preferable if it can be controlled. What you want to avoid are those chips from getting compacted or clogged in the flutes of the drill. That will make it more difficult for you to drill the holes and eventually impossible.

You can try peck drilling your holes. The action of drilling down a short distance and then briefly pulling the drill upward slightly(distance upward depends on what works best in that situation). The upward retraction tends to break the chip away from the part making a smaller chip. Also, a bright drill(shiny/polished flutes(no black coating)) will help with the flow of the chips up the flutes and out of the way for more.

Here’s an animation: peck drill


Agree with Blacksmith37. Note also that aluminum machining processes commonly use an oil-and-water emulsion called "mouse milk" as a lubricant, with a pump-driven feed nozzle aimed right at the hole, and a sump system that catches the used fluid and recycles it through a storage vessel and back to the nozzle again. If you are drilling thousands of holes and feeding the bits fast, you might consider this to prolong the life of your bits.


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