Burning out drill bits left and right

Chiro75

Chiro75

Joined
Feb 4, 1999
Messages
5,786
Letely I have been having no luck with drilling. I think I know what the problem is, but here is a breakdown of what I do. Let me know your opinion:

1) Rough profile blade on bench grinder. Probably overheating steel when I do this.

2) Grind, finish, etc. Then edge quench in oil and triple temper.

3) Drill.

I figured because of the differential heat treat that the tang is dead soft, but it probably isn't, is it? I burn out a 1/4" bit (HSS) without even breaking through 1/8" thick 1084. I can only get about 3-4 holes out of a 1/8" bit, too. Probably the steel is hardening a bit during grinding and a lot more than I suspected during heat treat. I like to drill as late as possible, though, in case someone wants an integral. I guess I'll just have to change my order of doing things. Also, when I drill handle materials I use a board under the material to minimize break through with the bit. It seems like I have better luck with steel by not using a board under it. Is this the right way to do it? I end up with a big gnarly thing I have to file off, but it seems easier on the bits. Am I right or wrong? And for reference, I am using a cheap Asian machine slowed down as far as it will allow with HSS bits.
 
Why would you wait till after heat treat to drill? Only way I can drill a hardened blade is with carbide bits and those buggers cost a fortune.
 
Like I said, I do an oil quench, so I assumed the tang was staying in the annealed state. I guess I was wrong! The reason I was putting off drilling as long as possible is that I wanted to give buyer the options of having the knives as integrals, so I fifn't want holes in the tang until I knew I was going to slap scales on them. Dumb Idea, I guess! Probably answered my own question...
 
Some billits come with a spring temper. Try annealing it prior to working it. Then tang should be soft after heat treat.
 
Chiro

After you grind normalize the whole knife 1 time to relieve any
grinding stress and then heat only the blade
to harden, if you edge quench you might get a little hardening around
the riccasso but it shouldn't be hard enough to cause drilling problems, if it is the blade might fail under stress at the tang and riccasso area.Always keep that area moderatly soft.
I don't drill until after I heat treat but I make mostly hidden
tang or threaded tang knives, so I like to fit the guard permanently
before I start my handles, I know some makers like to fit everything together before they heat treat and then assemble but I just don't have the luck of getting things back together as nicely as they were the first time so I wait.I rarely have any trouble drilling.Hope this helps, what works for one might sound stupid to others but we all have our own opinions and techniques.
 
Chiro, You should be normalizing and annealing your steel for the easiest drilling. It is nice and soft after annealing. You can drill it like butter. Your method is leaving a spring like temper in the middle where the holes go. The edge is hard the back is still soft but the center is spring. Cobalt bits and flooding with coolant may let you get away with it. It doesnt get hard during grinding unless you are getting it really hot and quenching in water.
 
Bruce, guilty as charged. I get it hot during grinding, but only during profiling since I do the rest with files. How do I go about annealing and normalizing? I assume it requires more equipment than what I am currently using (a few propane torches and some olive oil).
 
I believe. Just drilling 1/2" skeletonizing holes in 1/8" 1084 caused it to harden (I was probably drilling too fast) so that I couldn't finish the last of 4 holes!
 
Even if you have left the tang unhardened, as others have observed, it may be harder than you think! Wrap the blade in a wet rag and clamp it in a vice and "draw the temper" in the tang with your propane torch. I say draw the temper but of course its never been really hardened. heat it up all the way past blue to grey and let it cool. do this a couple of time, and you should find it much easier to drill. You're just getting rid of any wee little bit of hardness. Also be SURE your drill bits are sharp. resharpen for every hole if needed. You can sharpen a drill bit good enough by hand on an oil stone with practice. a fresh edge on the drill makes a big dif.
 
The 1084 and 1095 I got from TKS has been partially hard. The outer layers are soft, but the inside is fairly hard, and kills bits really quickly. I torch the hole areas to anneal it a bit and that works pretty good.
 
also try a cutting oil on the bit as you drill.

you need to learn to sharpen your own bits The time invested learning is worth it. It will save you a fair amount of money in the long run.:)
 
If you are forging your blades you will have to normalize and anneal before drilling. It sounds like you are doing stock removal, if so, it is more than likely already soft and ready to drill. Just grinding the profile isnt going to harden the tang. Use a pilot bit and be sure to cool as you drill at slowist speed. Dull bits require too much pressure to drill and there is massive heat building and it will harden quickly in the hole. Order cobalt bits and some coolant. Learn to sharpen them. They will last for years.
 
Check out Wayne Goddard's "One Brick Forge" for hardening. It's in Blade, if you don't have his books (recomended!).
Later, Lynn
 
CL, damn, it worked! Thanks! :barf:

Lynn- that is a good book. I'm too lazy to look for a supplier of refractory materials around here. Very, very lazy.;)

Thanks for the ideas, guys. I'll have to try some of these things and see what happens!
 
And make sure to clamp down whatever blade you are drilling first. Those things have been known to start doing a twirlybird effect on your hand. Dont ask me how I know this! :)
 
hi rob, i havent talked to you in a while, i got a knife ready for heat treat, i'll give you a call before sending it your way.
 
Steve,
As you can tell, I was just joking with you but I had a neighbor one time that really did that. He was drilling some holes in his aluminum boat to mount a running light. He came over to borrow a "sharp" drill bit. He just couldn't figure out why ALL of his drill bits were suddenly dull!

C Wilkins
 
There's a recipe for trouble! Take a guy who doesn't know which way bits cut, hand him a drill and a set of drill bits, and put him in a vessel that needs to be float-worthy! Did he sink when he hit the water? :cool:
 
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