Home Forums Hunting & Shooting Hunter's Campfire Does anyone know how to heat treat old drill bits.

I'm drilling tool steel, and I dull a lot of bits. I bought a drill doctor and can sharpen them right back up again. They drill wood fine, but back to steel, they do nothing but spin. I heat treat in a knife kiln up to 2200 degrees. I wonder if there would be a way to treat, and if necessary, temper the bits so they would cut steel again. I dulled a carbide drilling D2 and never tried another carbide for $40. I would do fine if I could resharpen regular bits and treat them so they would cut again. I wonder if anyone ever tried it.

If they're quality bits they're probably made from O1.

Heat the tip of one cherry red with a propane torch,..get it glowing bright enough that the surface begins to flake, (very bright!) then quickly dunk it in some old motor oil.

Stand back when ya dunk it and don't have anything flammable close to it. It's going to *poof* a flame up when it hits the oil.

If it's made from 01, the cat won't be able ta scratch it when you get it out of the oil.

By the way,..run the drill slow and keep a dab of dark thread cutting oil on it when you're drilling.

Run it too fast and it'll work harden the steel you're trying to drill through. D2 is especially tough to work.

Correct speed and plenty of oil, don't let them get dull and re-sharpen at the first signs of reduced cutting.

Never used a drill doctor and don't know if they grind well or not, always re-sharpened mine by hand and always grind a relief on the back side to help break up the chips.

Bristoe is dead on with the heat treatment, but can't ever remember the need to heat treat a drill to re-sharpen. But have done plenty of chisels and star drills like that.




Phil

What he said. Try drilling no faster that 50 SFPM. * Also try hand sharpening them to around 118 Deg included angle and splitting the point. You can sharpen a drill by hand better than a drill dr will do it. If the chips are blue you are turning the drill too fast.


* SFPM = Surface Feet Per Minute. To calculate SFPM it is the recommended cutting speed times four divided by the diameter. That would be in this case SFPM = 50 times four /divided by drill diameter. Say for a 1/4" drill it would be 50X4/.25 = 200 RPM.

Damn Scott, is there any thing you don't know? Impressive once again.

Have had good luck with Cobalt drill bits (good quality ones not home center ones) but they are brittle and the edge will chip if not fed under control. With hss bits, you may try slower speed, higher pressure and plenty of cutting oil or coolant. Might be work hardening the steel you"re trying to cut. Hope you're using a drill press and not a hand drill.

What are you drilling with...hand drill, drill press, mill?

What dia. ?

D2 in it's soft state is very easy to machine. When it's hard you can't cut it with HSS.

Sorry if I'm off base but aren't decent twist drills made out of high speed steel. In which case, wouldn't it be unnecessary to re-harden them if run slow and CAREFULLY sharpened?

I figured that I took the temper out of them drilling tool steel too many times.

I'm not familiar with the formula, but as written it is equal to 800 RPM.

Sounds like you did. Might as well try to harden it; though if it's HSS I'm not sure it's as easy to properly do as Bristoe described for O-1.

Just goes to prove you don't have to be smart to be a machinist.

Thanks for keeping me straight. The formula is just a rule of thumb. It simplifies the math from using Pi to figure circumference of the drill. It works for any turning situation. When drilling or milling it is the diameter of the tool, when turning in a lathe you use the diameter of the piece being turned. It is not a hard and fast rule but it is a good place to start.

The recommended cutting speeds for many materials can be found in the Machineries Handbook. I took the 50 SFPM for D2 from memory. I am not a hundred percent sure that is right.

It ain't,....and you CAN sharpen HSS to the point of them glowing RED,....They'll settle down and cut as good as the day you bought them.

GTC

Ten years ago I was a machinist my trade. Then I got hurt and had to find other work. I can no longer bend over a lathe or mill and standing in one spot all day on a concrete floor is out of the question. I am not really all that smart, Rob just asked a question I know the answer. Some things never go away.

Get a GOOD balnced Medium grit wheel and LEARN to sharpen "Offhand" on it with a steady rest for the back of one (gloved) hand,...and eye / respiratory protection, as well.

I OWN a couple or Three thousand "Drill Bits",....and find it WAY cheaper to just replace the small "Number Drills" than to fight with sharpening em'.....

If you're drilling a LOT of "Tool Steel" maybe you should be looking in a new direction,....Carbide is NOT "Rocket Science".

GTC

One of my first lessons in collage machine shop was how to off hand sharpen a drill bit. It must have taken. I can still offhand sharpen a 1/8 bit and split the point. Just one of those things I took to real easy.

Scott,....I was talking about WEE "Number drills",....nothing as large as .125".

You get a receiver, or barrel drilled / tapped at my place it's $25 a HOLE. (check Brownell's national Averages, that is NOT particularly "High")

I damn sure (at that price) afford a new bit or two, and am not real stingy about buying new TAPS,....either.

There's regular "Holes" and than there's the other kind, the DEAD NUTS kind.

"Hole making" is THE most dominant workplace feature in Modern American Machine shop practice,.......VOLUMES are available, should one wish to pursue the subject

Have bored holes to a unilateral 0.0002 on parts square, parallel and to size of the same tolerance. Time was that was my everyday job. The company was great. They knew those tolerances take time and they understood no one could do it every time. I remember throwing away a part I had worked on for a week when I blew a tolerance and the foreman just shrugged and said to make another. Attitudes like that make precision work a joy.

I also am a believer it throwing away a tap before it breaks. A lot cheaper in the long run.

The BEST Bits I've known were by a Company called "Butterfield".

Long run of Copper / Nickel ("Carra-Dur") valve guides.

The "Basic" bit that we chose cost about $15.00 a pop, in quantities of 50. Some would make 25-30 holes,....some would give up on the first part.

One thing I learned from Butterfield's "Tech Rep", a verifier at 30 + years of chewing on metal,
.....HIT the damn work piece turning and MAKE a hole .

If you have to "Sneak up on a cut" something's wrong.

Larger holes,....I'm a BIG fan of the Rota-broach / Ream method, been using it on Soil Engagement pieces,..... Cutting edges and such (HARD chit)

The new "Indexables" are worth along look, too.

Fast, and cost efficient v. "Bits"

GTC