dbooksta
Plastic
- Joined
- Sep 28, 2016
- Location
- Philly suburbs
With great difficulty I used a cobalt bit to drill a 1/4" pilot hole in this 3/4"-thick steel (which I assume is mild, but which could be hardened). Now I'm trying to cut the finished 1/2" hole using a brand-new cobalt 1/2" bit and after many minutes of pecking and stopping to add water-based lube (which isn't boiling, so it's not a heat problem), I've barely gotten the full tip width into the hole.
I've tried running at 620rpm, 1100rpm, and 1720rpm. I've tried applying more force and less force. Essentially, the bit is hardly cutting. Figuring I must be doing something obviously wrong, I just stopped, took the following video at 1100rpm (where you can see how easily I can stop the bit with pressure), and am wondering if someone can give me any ideas on how to more effectively drill this steel?
Attempting 1/2" drill in mild steel - YouTube
I've tried running at 620rpm, 1100rpm, and 1720rpm. I've tried applying more force and less force. Essentially, the bit is hardly cutting. Figuring I must be doing something obviously wrong, I just stopped, took the following video at 1100rpm (where you can see how easily I can stop the bit with pressure), and am wondering if someone can give me any ideas on how to more effectively drill this steel?
Attempting 1/2" drill in mild steel - YouTube