Recommended drill bits for hardened steel?

[chim]

I could be wrong, but other than that snow plow edge I'd guess most stuff on the farm won't be too hard. Other that the hardened wear/working parts a lot of the steel used for framework or holding the hard parts should be softer.

 

[shock]

I could be wrong, but other than that snow plow edge I'd guess most stuff on the farm won't be too hard. Other that the hardened wear/working parts a lot of the steel used for framework or holding the hard parts should be softer.

Does that mean I should be able to get by with HSS or Cobalt for the majority?

 

[jyoutz]

Does that mean I should be able to get by with HSS or Cobalt for the majority?

I believe cobalt is the best you can get.

 

[chim]

Does that mean I should be able to get by with HSS or Cobalt for the majority?

My training is in electrical and mechanical trades. I'm no machinist who can figure out the best RPM and bit for every application. There are other people on board here who can. Recently I've been using DeWalt TiN pilot point bits. Have used more black oxide previously.

For most of the drilling I've done over the years HSS bits worked fine. I worked with carbon steel and haven't drilled any stainless thicker than maybe 12ga. Never had to drill grader blades or hardened steel.

For larger diameter holes I've used hole saws. For up to 16ga sheet metal that was mostly without any lube. For thicker metal I used either oil or even water. Several years ago I needed some 1" holes in 1/2" thick carbon steel and used a hole saw in a battery drill with a slow stream of water from a garden hose to lube and flush. I really like using an impact driver with a hole saw because when the hole saw catches it won't twist you wrist. With my drivers that works up till about 1-1/2" diameter.

A couple years ago I finally lucked into a decent 3/4" drill press and also bought a mag drill and annular cutters. Both were very welcome additions.

 

[sandman2234]

Cobalt is not the best you can buy...heck, carbide is a lot tougher than cobalt! Diamond tips are even better, but now your talking serious money. However, carbide requires a steady pressure and even feed. It is very brittle and will chip or crack at the blink of an eye! A slow drill press or a milling machine with the correct feeds and speeds work better with it.
One of the things I tend to shy away from is drilling stainless steel with a hand drill! Even with a drill press it can be a challenge! Work hardens in an instance! If you really want something that is even more fun to drill, grab a piece of titanium and try to drill it without the exact speeds and feeds for it! Work hardens faster than stainless, and becomes a nightmare once you let off the feed or speed!
Good luck, and study up on speeds and feeds for different grades of metals and your drilling will improve faster than you would think!
David from jax

 

[ArlyA]

Cobalt is a better grade of HSS which I own many of. It is good but more venerable to chipping.

 

[DarkBlack]

Tungsten carbide for hardened metals

Cobalt is a premium HHS for unhardened materials.

 

[Hay Dude]

Cobalt is not the best you can buy...heck, carbide is a lot tougher than cobalt! Diamond tips are even better, but now your talking serious money. However, carbide requires a steady pressure and even feed. It is very brittle and will chip or crack at the blink of an eye! A slow drill press or a milling machine with the correct feeds and speeds work better with it.
One of the things I tend to shy away from is drilling stainless steel with a hand drill! Even with a drill press it can be a challenge! Work hardens in an instance! If you really want something that is even more fun to drill, grab a piece of titanium and try to drill it without the exact speeds and feeds for it! Work hardens faster than stainless, and becomes a nightmare once you let off the feed or speed!
Good luck, and study up on speeds and feeds for different grades of metals and your drilling will improve faster than you would think!
David from jax

I just went through a big job of replacing outer truck frame (double frame) on my dump truck and learned a lot about drill bits. Good ones are not cheap. I tried “quality” bits to drill 1/2” or larger holes and they were junk quickly, even with proper RPM and lube. I then acquired some good quality bits from an Amish machine shop and finished the job easily.
Stepping up in size and pilot holes was the key for me. It was hard steel 11/32” thick and double that because it’s 2 frames overlaid. Many holes to drill for tool box mounts, too.

 

[NoTrespassing]

Does that mean I should be able to get by with HSS or Cobalt for the majority?

What diameter and depth do you need to drill? A center drill or center punch, then a pilot hole can be helpful, use the shortest bit you can like a screw machine length (SML) bit. https://www.mscdirect.com/products/drill-bits?rdrct=drill bits

 

[shock]

Thanks for the replies guys. I already learned a lot more than I knew yesterday. You have to start somewhere, right?
I have a variety of jobs that I'm always drilling something at the farm, so I don't have a specific job in mind with this question. I think about the things I've drilled in the past and probably will do more of the same in the future.