Countersink bits for metal

[MikeG]

Tap Magic for Aluminum. Expensive, but the stuff really works.......

 

[sgtsandman]

Depending on the application, chatter marks could be a cause for leaks as well since the screw can’t seat flush in the counter sink.

 

[ericbphoto]

Use thinner cutting oil for aluminum.

What does speed have to do with then?

Speed has everything to do with how any cutter works. The speed the cutter rotates and the speed that you feed it into the work material. You can calculate the best speeds. It's in any machinists handbook and online. Generally, larger cutters = slower speeds. Once you experience a good quality cutter at the proper speeds with the proper lubricant, you WILL be convinced.

 

[Dirtman]

I don't use oil with aluminum. I use coolant.

 

[sgtsandman]

Coolant still has a lubricant in it before anyone asks. So, Dirman’s comment is valid.

 

[cbxer55]

Use thinner cutting oil for aluminum.


Speed has everything to do with how any cutter works. The speed the cutter rotates and the speed that you feed it into the work material. You can calculate the best speeds. It's in any machinists handbook and online. Generally, larger cutters = slower speeds. Once you experience a good quality cutter at the proper speeds with the proper lubricant, you WILL be convinced.

Precisely. At work we simply call it Feeds and Speeds. Aluminum, faster with less pressure. Titanium, very slow with high pressure. And with countersink bits, I have less chatter problem if I run them slower than I would a drill bit.

 

[Eddo Rogue]

Update: I bought a 3/4" carbide 6 flute, used medium/slow speed on drill press and tapmagic. The workpiece was secured but not clamped as it was big and heavy (6' length of 3"x5" angle iron 3/16" thick). It turned out beautiful. Thanks everyone for tips, tricks and recommendations.