Bit Hardness

[CanDo]

Hey guys,
This isn't quite about knifemaking, but you are the right people to ask. How hard are drill bits on the rockwell C? I understand they probably differ a lot, but I'm interested in anything - cheap wood bits, 'carbide' bits, etc. I am wondering if one would be suitable to steel a larger blade between honings.

Thanks,
CanDo

 

[Nathan the Machinist]

Drill bits are usually made of a high speed steel such as M2. Other high speed steel cutters such as lathe bits and saw blades are usually very hard, such as HRC 65. I expect a drill bit is too, but I don't know for sure.

The shank of a brazed carbide bit, such as used in concrete drilling, will probably be fairly soft.

The shank of a carbide drill (carbide) is much harder than can be achieved in steel. I don't know what the HR number is, but it is way up there.

 

[CanDo]

Alright, that's what I was hoping. Thank you for the information, I'll try it out once I have a big blade to steel

 

[J S Machine]

Most HSS drills are around 64-65 RC. When you use enough of them in a machine shop or a tool/die shop, you run into a soft one every now and then...kind of weird when the sucker just dulls almost instantly when drilling something tough...Your best bet is to get one that has "HSS USA" on the shank as opposed to "HSS CHINA" for obvious reasons. They make Titanium coated drills too, and some other types of coatings.--most apear gold or dull gray. I've heard that the coating itself is close to 90 RC, although I don't believe it.

Carbide drills are way up there as Nathan said, but they are very brittle. I only use a carbide drill if I am working with something like Inconel or some other tough a$$ unmachinable stuff. I usually take a piece of carbide and grind it to cut like I want it to. A broken piece of carbide is treasure to me, because I can usually make something out of it that will cut. They are very expensive too, so it's best to be resourceful with them lol...

I've tested drills, on a hardness scale, to figure out if I could use them for certain jobs. I often grind drills too to cut different materials. For instance, a slightly dull drill will cut copper better than a brand new sharp one, because the new one will grab and break. A 3 flute also works well for metals like copper too..good luck finding one though.