Countersink Holes in Aluminum

[Mark Blatter]

I am working on a different style of book cases that have aluminum on them. I am thinking of either 1/16" or 1/8" but haven't decided yet. I will need to countersink the screws and was testing it out this weekend. I kept getting burs on topside of the aluminum and push through on the bottom side.

I did some reading of past threads here and elsewhere and cannot seem to find a good answer. I have tried both the countersinks with pilot drills and just the countersink. Neither seems to work much better than the other. The pilot bit countersinks I used are brand new ones from Irwin.

Any suggestions or recommendations?

[Tom Howarth]

I've been using an old Craftsman "Vee" router bit for countersinking screws. Not a carbide one but a HSS one,
on wood not aluminum. I use it in my drill. I very found it's best to countersink, then drill the hole. Try it on a piece of scrap...
I'd probably use a center punch to keep it from wandering...

[ken masoumi]

A sharp countersink bit should do the trick ,I remember a few years ago doing hundreds of countersink holes in aluminum strips ,what worked was finding the right speed for the drill press and my own feed rate, also not to push down too hard .go up and down a few times to get to the final size,check your work and adjust your feedrate speed accordingly,that would be my suggestion.

[Bruce Page]

A sharp c'sink and let the tool do the work - don't push/force the cutter too hard.
Will you be using a hand drill or drill press?

[Mel Fulks]

Put some denatured alcohol in a squirt bottle and use that. Works very well. Cuts fast and clean ,stops all that aluminum gummyness. Using that the quality of the countersink tool is much less critical.

[Gene Takae]

This type makes exceptionally smooth countersinks in aluminum. The original is made by Weldon.329597

[Peter Quinn]

Google "center drill", that's what I use for aluminum. The bur's on the bottom side don't seem to be much trouble, you can work those out easily by sanding or running the center drill in just a bit from the back, or using a deburring counter sink from the back. A decent HSS center drill works well, best to test on scrap first.

Here's and example of the basic sequence i was taught. First is the center drill, then they punch the main hole with a basic drill bit, they clean up with a counter sink with multiple flutes, like a tapered deburring tool.

https://www.youtube.com/watch?v=wTjuq-IGX3k

[David Malicky]

Good advice above. Also:
The type of aluminum makes a difference. 3003 and 5005 are soft and make bigger burrs. 6061-T6 is less ductile, smaller burrs.
The rpm and feed pressure must let the tool take a reasonable cut -- not too light or heavy.
The single-hole Csinks like Gene posted tend to chatter the least, but they require more feed pressure.
To some extent, a burr is inevitable when cutting metal.

[Mark Blatter]

A sharp c'sink and let the tool do the work - don't push/force the cutter too hard.
Will you be using a hand drill or drill press?


Drill press.

[pat warner]

Clearly a dark art with 8 different answers.
But in my view, all have merit.
But I would add an A. Ford Uniflute CS to the mix.
Speed and feed critical. A cs without a hole will have less chatter, always a burr and on both sides of thin material.
Definitely drill press and one that works.
Lube will get the swarf off of the cutter and higher speeds will sling it off. It's a balancing act.
Samples of holes and countersinks (http://patwarner.com/images/work_aluminum2.jpg) (most are 82° ).

[Ellery Becnel]

Do not forget a rigid setup. If you have the best CS, feed, and RPM correct a weak setup will chatter. All good info.

[Ole Anderson]

Put some denatured alcohol in a squirt bottle and use that. Works very well. Cuts fast and clean ,stops all that aluminum gummyness. Using that the quality of the countersink tool is much less critical.

WD40 works fine also, never tried the alcohol.

[glenn bradley]

This type makes exceptionally smooth countersinks in aluminum. The original is made by Weldon.329597

Although I have others for different purposes, these are my go-to. My current ones are from Lee Valley. They sharpen easily and are very speed tolerant. I assume you are doing this in the drill press. As mentioned, check your speed.