Harbor Freight Cobalt Bits

I couldn't resist these

formatting link

115pc M35 4.8% Cobalt bits. They're not M42 8%, but they don't cost

600.00 either. I took a 1/4" M42 Cleveland Twist and a 1/4" HF bit and drilled two holes with my mini-mill using with each drill bit. Feed was heavy and slow, nonstop feed through a block of 1-1/2" thick steel plate. I then inspected each cutting tip under a loupe. The CTwist cutting lips were mangled 1/3rd as much as the HF, BUT I swear the HF wanted to cut 50% easier and faster than the CTwist bit even with one cutting lip mangled (by unremoved swarf I guess). Using a scratch test, I found the HF bit to be harder than the CTwist bit believe it or not. It certainly was not easier to sharpen. I was REALLY impressed by these HF bits.(Not their other bit models though). I guestimate I could have drilled through 4" of steel before needing to resharpen the HF bit. Going by wear, I'd say the CTwist bit would drill through 12" of steel , with higher needed feed pressure, before needing to be resharpened. Still, not bad for an M35 bit (versus the higher cobalt content of the M42 CTwist). For non-production uses, I'd say the drills are a great buy. Having to resharpen the bit after every 4" thick hole I drill is not bad IMHO. The drills were put into a spare 115pc Huot case and all the sizes seem accurate (except for about the 10 smallest bits (#50 through #60). They seemed to be less precisely sized. I'm pretty impressed with them.

We routinely drill hundreds of inches of holes with simple high speed American made bits. In fact, ran a job two weeks ago where we drilled a

3/16" hole in 3/4" steel bars and drilled 920 holes w/o looking a the drill point. A point to remember is that breaking out is normally the cause of drill failure. If you don't break through the far side it will last nearly forever, given the right feeds and speeds. Apparently it doesn't take much to impress you as drill diameter is sometimes more important then the number of holes you can drill. There is no way to measure the diameter a drill will drill except by measuring the holes it has drilled. That takes pretty good measuring tools too, like ground pins for the smaller sizes. Leigh at MarMachine