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