Recommended drill bits for hardened steel?

[LouNY]

I'm not a machinist by any means, that said.
I used to do a lot of drilling, tapping, a bit of milling work, and small turning on an old lathe.
My go to lubricant has been a blend of diesel and cheap ATF for years.

 

[CliffordK]

I free hand sharpen my bits, and they'll work for a while. I'm not sure I've found formal instructions. But, I like to match the angles, and add a little angle from the trailing edge to the leading edge.

 

[5030]

The toughest and hardest drills you can buy are Hi-Roc die reclaim drills. You can even drill glass with them. They are very expensive and the only lubricant - coolant you need with them is water. I have a set of them for drilling hardened tool steel.

Cobalt and Titanium Nitride (Tin) drills are just high speed drills with a coating on them that promotes chip flow and nothing else. Myself, for general drilling, I just use plain (bright finish) HSS drills with the correct speed and feed and lubricant, and I offhand sharpen all my drills, well all the larger ones. The small ones (under 1/8") I just replace them when they get dull and I use a drill gage to hold the correct cutting angle when grinding them. I use all screw machine length (stubby) drills in my mag drill because of the limited clearance between the quill and the mag base and screw machine length drills are much more rigid as well. Just don't buy cheap Chinese knockoff drills, stick with domestic made drills, I tend to use Chicago Latrobe (Greenfield Manufacturing) or Cleveland Twist. Neither are cheap but with drills, you get what you pay for. Actually, Greenfield now owns Cleveland Twist, FYI.

 

[Mike1955]

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.

Thank you Koza for that. I’ve drilled all my life using oil. I’m going to tractor supply for some tap magic. Maybe save. Some sharping time!

 

[5030]

I don't believe you'll find Tap Magic at any tractor supply store but I could be wrong.

Any boundary, free flowing lubricant will work however, not just Tap Magic.

 

[chim]

Got mine online along with Stick-Kut at Amazon.

 

[5030]

Most people, I'd say 95% of people that drill stuff using conventional 118 degree or 135 degree twist drills, don't have a clue how to sharpen them correctly with offhand sharpening. In reality, it's a coordinated 2 hand operation to apply the correct cutting angle while grinding the chip relief and getting the web correctly orientated. Not something you can easily accomplish, it takes lots of practice as well as well as a drill angle gage to get the cutting edges parallel and cutting the same (depth of cut and uniform chip removal). Kind of like TIG welding, not a assumed trait but a practiced one.

I've seen some real buggered jobs on improperly sharpened twist drills and most time the boogered drill won't cut anyway.

The inherent issue with an improperly sharpened twist drill (besides the fact that they won't cut) is if the cutting angles on each flute as mis- matched, the drill will produce an oversized (oval) hole as the cutting edges aren't taking an equal bite of the material and if the heel isn't negative relief, the chip flow is impeded, consequently, the drill won't cut.

Like I stated, 95% of users are incapable of correctly sharpening a twist drill where it will actually cut properly and most won't cut at all.

There is a solution however. Get yourself a Drill Doctor and use that to sharpen twist drills. It won't sharpen all of them but will sharpen the most common sizes under 1/2" diameter.

There is another (though more costly alternative and that is the Vevor drill sharpening machine. It uses ER (extended range collets so you can sharpen both metric and SAE drills and it does a fantastic job but it ain't cheap and unlike the Drill Doctor, the Vevor sharpener will relieve the heel as well and it will sharpen Tungsten Carbide tipped bits as well as it comes with a diamond impregnated sharpening wheel as well.

Both are better than a boogered up hand sharpening job by someone that lacks the 2 handed skill to properly sharpen a twist drill.

I never throw them away when they get dull. I resharpen them until there isn't enough flute left to be any good anymore.

I'm always getting dull drills dropped off at the shop to get ground, mostly large diameter, reduced shank S&D drills.

My dad taught me how to hand sharpen twist drills decades ago. Glad he did as it's saved me a ton of money over the years.

 

[5030]

I sharpen my own end mills as well but they get sharpened in a special fixture that is clamped to the magnet table on one of my surface grinders. The cutting edges on an end mill must be ground at a consistent height as well as have the proper heel relief as well and they have to be sharpened (ground) in a special holding fixture that grinds all the cutting edges with a consistent height. Impossible to do by hand.

 

[farmideas]

Need to get some drill bits for around the farm. Thinking cobalt?

You're thinking is right! I bought 3% cobalt bits for the more frequent hole sizes and used a Practool adjustable for holes from 1/2in to 2 inches. Cobalt is expensive but is well worth it for ease of use, durability and more. I recommend it to readers of www.farmideas.co.uk

 

[JONNY BOYYY]

Need to get some drill bits for around the farm. Thinking cobalt?

carbide bits..but go to the little extra expense and get good ones with a warranty

 

[jrsavoie]

Hardened steel is challenging to drill. Lots of oil when drilling is key. I like Champion, Viking, Norseman, and Cle-line drill bits.

I concur.
I've mostly used Norseman drill bits.

I've had good luck with stainless, triggering the bit.- repeatedly pulling the trigger and letting off.

Pulling the trigger wide open is the biggest mistake most people make.

Had an electrician, that just smoked 3 bits, ask what kind of bits I was using. He was using the same Fastenal gold bits that I was. Those were Norseman - at least back then.

I showed him on a couple holes. To no avail.

 

[jgmo]

The best bits in the world will be damaged if not used correctly. Slower drill speed, steady pressure and cutting oil are the basic "good practice" things to strive for. I like to stop frequently and feel the drill tip. If it is getting so hot you can't keep your finger and thumb on it, you're either going too fast or pressing too hard or both.

I knew a great machinist when I was a buck that would sharpen my cobalts for me so they cut like butter.

I still kick myself for not paying closer attention to his wisdom and learning the tricks he was willing to share.

But, I was still young n dumb n full o want some.

If you come across somebody like that, don't be like me.

PAY ATTENTION!

And, I will leave you with....

If you ever need to "dig out of a hole", as in removing a broken bolt or, worse, drill out a broken off EZ out.....

Two words: Rescue Bit.

Expensive but worth every penny when needed Just make dang sure that you follow THEIR directions.

Good luck

 

[Flogger]

I use Harbor freight drill bits and keep windshield washer solution in a spray bottle. The steel you encounter on equipment is rarely hardened unless it is a ground engagement part. The windshield washer solution keeps bits very cool and a blow gun is all that's needed to clean up the mess. The good thing about Harbor Freight bits is if you need to drill a 90° hole you just bend the bit to the shape needed. (Just kidding. Craftsman are the flexible ones!)

 

[Flogger]

Most people, I'd say 95% of people that drill stuff using conventional 118 degree or 135 degree twist drills, don't have a clue how to sharpen them correctly with offhand sharpening. In reality, it's a coordinated 2 hand operation to apply the correct cutting angle while grinding the chip relief and getting the web correctly orientated. Not something you can easily accomplish, it takes lots of practice as well as well as a drill angle gage to get the cutting edges parallel and cutting the same (depth of cut and uniform chip removal). Kind of like TIG welding, not a assumed trait but a practiced one.

I've seen some real buggered jobs on improperly sharpened twist drills and most time the boogered drill won't cut anyway.

The inherent issue with an improperly sharpened twist drill (besides the fact that they won't cut) is if the cutting angles on each flute as mis- matched, the drill will produce an oversized (oval) hole as the cutting edges aren't taking an equal bite of the material and if the heel isn't negative relief, the chip flow is impeded, consequently, the drill won't cut.

Like I stated, 95% of users are incapable of correctly sharpening a twist drill where it will actually cut properly and most won't cut at all.

There is a solution however. Get yourself a Drill Doctor and use that to sharpen twist drills. It won't sharpen all of them but will sharpen the most common sizes under 1/2" diameter.

There is another (though more costly alternative and that is the Vevor drill sharpening machine. It uses ER (extended range collets so you can sharpen both metric and SAE drills and it does a fantastic job but it ain't cheap and unlike the Drill Doctor, the Vevor sharpener will relieve the heel as well and it will sharpen Tungsten Carbide tipped bits as well as it comes with a diamond impregnated sharpening wheel as well.

Both are better than a boogered up hand sharpening job by someone that lacks the 2 handed skill to properly sharpen a twist drill.

I never throw them away when they get dull. I resharpen them until there isn't enough flute left to be any good anymore.

I'm always getting dull drills dropped off at the shop to get ground, mostly large diameter, reduced shank S&D drills.

My dad taught me how to hand sharpen twist drills decades ago. Glad he did as it's saved me a ton of money over the years.

My Drill Doc goes to 3/4". Right handy tool.

 

[5030]

Darex makes a good machine but the Vevor is better. It's also 3 times the price. If you really want to spend big bucks, Darex makes a 'professional' drill and end mill grinder that sells for around 5 grand.

 

[Fields_mj]

I spent 6 years working as a machinist many years ago. My opinion is this. For hardened steel, you need carbide. Problem is that carbine is extremely brittle. It does not take impacts or bending moments very well meaning that if you're using it in a hand drill, there's a good chance you'll damage it LONG before you wear it out. If you're only doing one hole, a masonry bit is usually the cheapest option. If you're using a drill press, carbide will hold up better, but you still need to use the right speeds and feeds, and lots of coolant. For tinkering around in the garage with ordinary steel, I normally use ATF, but motor oil will work too. I need to cut hardened steel, I would find something better.

 

[Bentrim]

I had to dril out a hardened bolt a long time ago and was told to use masonary bits. They popped and twisted a bit but did drill thru the hard steel.

 

[5030]

Like I stated previously, Hi-Roc die reclaim drills. Not cheap however. You can even drill glass with them.

 

[pacosperson]

Need to get some drill bits for around the farm. Thinking cobalt?

Nearly all ag implements are tough, not hard. If hard they would be more likely to break under the common and various shock loads the experience in use. A common hand file will tell you enough. If the file cuts the material, you can very likely drill it. If the file simply does not bite in, you would need special equipment you do not possess. It's a simple, reliable 10 second test.
In drilling you must have coolant. Some specialty oils are made just for drilling steel and are available in most hardware stores. Likely in the plumbing section. Plumbers still cut and thread a lot of pipe.
Drilling is a cutting operation. Once you get a chip started, keep it going. You want to cut away the material, not wear it away.
Learn how to properly sharpen a drill. You will ruin many developing that skill, but it lasts a lifetime. Many drilling problems are due to improperly sharpened drills.

 

[5030]

Many drilling problems are due to improperly sharpened drills.

Not many, MOST. That and pushing a dull drill which does nothing but workharden the drilled material and give you a sore arm.

I rarely allude to it on any forum but, I hold a Journeyman's card in tool and die making and I just happen to own my own short run machine and fabrication shop and yes, I also have full time employees.

Offhand drill sharpening is a learned skill and it takes time to learn and master it. There are some pretty good vids on YT that go into off hand sharpening.

I still sharpen all mine down to 1/8". Below 1/8" I just buy new ones. No matter what you do, you still need a drill angle gage to check them.