Recommended drill bits for hardened steel?

[jyoutz]

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 had a brain fart last night when I posted. I meant to say carbide.

 

[CliffordK]

Project Farm did a piece on drill bits. I believe that he attempted to drill various metals including some rather hard metal.

If you are drilling hard steel, then expect to either resharpen or replace bits frequently.

 

[ArlyA]

Project Farm did a piece on drill bits. I believe that he attempted to drill various metals including some rather hard metal.

If you are drilling hard steel, then expect to either resharpen or replace bits frequently.

I love his practical testing.

 

[LouNY]

I have purchased drill bits from here;
Drill Hog®
several times, seems to be decent prices and the bits a decent quality.

 

[Williy]

IMHO you should use some cutting oil when drilling metal

willy

 

[shock]

That was a great video and helped me tremendously. I've narrowed it down to a few sets. Thank you folks!

 

[etpm]

My Bona Fides: I am a retired machinist with about 50 years total experience with about 30 years experience owning my own shop. I would say that cobalt HSS drills are the best choice for what you want to do. Buying high quality drills will pay off in the end. Precision Twist Drill is a good brand. But any brand that MSC sells will be good. Don't be fooled by TiN coated drills. Even though the TiN coating is very good at resisting wear and is also quite slick it needs to be of sufficient thickness to work well. The problem is that there are a lot of cheap drills and other cheap cutting tools that have a coating that is way too thin to have any positive effect. So don't be fooled just because the drill has TiN coating, the drill must also be a high quality to begin with.
If you don't need a long drill then don't use a long drill. The best short drills are going to be Screw Machine Length, AKA Stub Length. The best point is a Split Point. These are the most common point for stub or screw machine length. They center better and require less pressure to penetrate the work.
You must use cutting oil for good tool life and least effort. Don't use motor oil, it is a bad cutting oil and will shorten tool life considerably. Any decent hardware store sells thread cutting oil is small containers. It has sulfur in it which is good for the high pressures encountered when drilling hard metals. There are better cutting oils but the stuff sold in the hardware store is commonly available almost everywhere. If you buy drills from MSC you can also buy some cutting oil from them.
When drilling tough steels to get the best results the drill must be spun at low RPM and the pressure must be kept high. There must always be a chip formed while drilling. It is best to keep the chips from being blue. If the drill stops cutting then either increase the pressure or stop drilling. There are lots of charts online that have the proper RPM for material and drill diameter. Use these for a guideline but try to keep the RPM a little lower. Remember, for your situation, it is better keep the drill spinning slower. This is because with a hand drill it is easy to get the drill spinning too fast. Also, when the drill starts to break through the work back off on the pressure. This will help prevent chipping the drill point.
So, to sum things up, use cobalt split point stub length drills, low RPM, high pressure, and cutting oil. And back off the pressure as the drill breaks through.
Eric

 

[kozal01]

A lot of good info here. As a former tool and die maker and CNC machinist myself my one last piece of advice is to use a quality cutting/ tapping fluid, tap magic is a reputable brand that you can usually find locally. It makes a big difference especially in hard to machine materials. Dont use engine oil, or WD40, or grease, or soap or anything else besides cutting oil. You would be shocked to see some of the nonsense some people use for cutting oil. I'm an apps engineer for a cutting tool company now days and it never ceases to amaze me when I see a customer take a high end drill or tap and try to use crisco, or bacon grease or some other crap that some dude 40 years ago told them to use.

 

[Sawyer Rob]

Tap Magic is some good stuff, I much prefer it.

SR

 

[shock]

My Bona Fides: I am a retired machinist with about 50 years total experience with about 30 years experience owning my own shop. I would say that cobalt HSS drills are the best choice for what you want to do. Buying high quality drills will pay off in the end. Precision Twist Drill is a good brand. But any brand that MSC sells will be good. Don't be fooled by TiN coated drills. Even though the TiN coating is very good at resisting wear and is also quite slick it needs to be of sufficient thickness to work well. The problem is that there are a lot of cheap drills and other cheap cutting tools that have a coating that is way too thin to have any positive effect. So don't be fooled just because the drill has TiN coating, the drill must also be a high quality to begin with.
If you don't need a long drill then don't use a long drill. The best short drills are going to be Screw Machine Length, AKA Stub Length. The best point is a Split Point. These are the most common point for stub or screw machine length. They center better and require less pressure to penetrate the work.
You must use cutting oil for good tool life and least effort. Don't use motor oil, it is a bad cutting oil and will shorten tool life considerably. Any decent hardware store sells thread cutting oil is small containers. It has sulfur in it which is good for the high pressures encountered when drilling hard metals. There are better cutting oils but the stuff sold in the hardware store is commonly available almost everywhere. If you buy drills from MSC you can also buy some cutting oil from them.
When drilling tough steels to get the best results the drill must be spun at low RPM and the pressure must be kept high. There must always be a chip formed while drilling. It is best to keep the chips from being blue. If the drill stops cutting then either increase the pressure or stop drilling. There are lots of charts online that have the proper RPM for material and drill diameter. Use these for a guideline but try to keep the RPM a little lower. Remember, for your situation, it is better keep the drill spinning slower. This is because with a hand drill it is easy to get the drill spinning too fast. Also, when the drill starts to break through the work back off on the pressure. This will help prevent chipping the drill point.
So, to sum things up, use cobalt split point stub length drills, low RPM, high pressure, and cutting oil. And back off the pressure as the drill breaks through.
Eric

This is excellent! Thank you for taking the time to educate me, and probably, others on here!!! A+++