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.043 Drilling A2 Tool steel


Oct 20, 2022
Hello! I’m new here, I came across a problem today when I had to drill a .043 hole .375 deep into an A2 tool steel plate. I used a .043 jobber drill that had a .5 loc which might’ve been too long but it managed to drill 10 holes and it then broke halfway into a hole. I was doing 14000rpm, 0.7 in. feed with a .025 peck using flood coolant of course. I then managed to get through the rest of the holes easier and faster using a .041 carbide drill 14000 rpm 2 in. feed with a .05 peck and repeating it with the .043 jobber drill at 5000 rpm 1 in. feed .05 peck to bring hole to size. Although I managed to figure out that the carbide drill works better, is there any other way, method or process that can get this done more efficiently? Thanks in advance for any answers!

Edit: I did spot the holes beforehand .083 90° because of a required countersink.


May 11, 2017
Minneapolis, MN, USA
Cheap but good carb micro drills:

Feed/speed calculator:

Carbide drills usually don't need a spot, and work better without one. Sink after.


Dec 14, 2017
I assume the first drill was HSS so at over 150 sfm you burnt up the drill. Probably should have used about a third the speed. At 2 IPM the chip load was .00014 IPR probably should be more like .0008 IPR.

I have run into crummy imported A2 that eats HSS drills and while this may have contributed to your trouble the main issue was bad speed and feed.

Find a reference for starting cutting speeds and start there. Almost always the manufacturer will provide good tech support.