Drill bits

C

cjensema

Joined
Dec 29, 1998
Messages
288
I am trying to drill some AST-34 steel using cobalt drill bits. I can drill 3/32 holes without a problem. I can't drill 3/16 or larger holes and wrecked three drill bits learning that. The 3/16 bits I have will drill my 440C and some of my AST-34, but not the batch of AST-34 I am working on now.

Am I correct in assuming that I need to get some carbide bits for this? What kind of carbide bits? The MSC catalog has many different kinds. Carbide bits are pricy... What's the cheapest place to get them?

What's the best drill bit for each of the various kinds of metal? Some general guidelines on drill bits from the experts would be helpful.

Thanks.

Carl
 
If your material is soft (before heat treat) Run your drill bit slower . It sounds like you running to fast. Also if your first drill is running to fast it will semi toughin the hole making the next drill burn up. Slow down and use coolant .
cool.gif

Use m2 drill also this helps . Cheap drill do a cheap job.
Carbide will work but is not nessesary.

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Web Site At www.infinet.com/~browzer/bldesmth.html
New Web at www.darrelralph.com

 
Carl: You should have no problem drilling annealed steel of ANY kind using cobalt bits, particularly new bits. Carbide bits are generally used only on heat treated material, and definitely require a drill press as a minimum to reduce breakage of the bit.
Are you using an electric drill or a drill press?
with a hand drill, it becomes more difficult to generate enough pressure on the bit to make it cut. The trick is to make a small hole and open it up, in steps if necessary.

I'd also recommend buying AMERICAN made bits, Chicago Latrobe, etc. as they are just better than the imports. Water works fine as a coolant, or a light oil of almost amy type.

You can probably resharpen the bits you have, and try again-sometimes the import bits just aren't sharpened properly.

Good Luck,

RJ Martin
 
Thanks, Darrel and RJ. That's good information. I suspect Darrel was right... I think I hardened the steel around the hole with my first drill and this caused the other two bits to fail. I used a drill press and it was set too fast the first time. I slowed it down for later drilling attempts, but the hole was already hardened.

Live and learn.... Thanks again.

Carl
 
Light oil of any type is usually the case. But once I grabbed a can of the new improved liquid wrench ( with Teflon!)This did not help my older drill bit get through that peice of hardened steel that was supposed to be holding my harrow together at all
smile.gif


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Fix it right the first time, use Baling Wire !
 
try using cutting fluid, it'll work better than plain old light oil. if your drill press can't go very slow, get a mist coolant system.
 
Sometimes soapy water works better than oil when drilling holes. Seems to make the bit bite better.
 
:
Regular twist drills are sharpened for general use.Usually for mild steel.
A bit more clearance ground on them makes them cut harder materials easier.That's what we did with the harder steels like 4130 and the harder stainless
steels like 304.
You can look at a new drill and note the chisel point angle.Increaseing this angle will give you more clearance.Just be careful not to get too much and make the cutting edges too thin.

You can take a drill that's "grabbing" on brass or other soft metals and grind a small flat on the edges and it will stop the problem.It also cts down on chatter if that's a problem.
Hope this helps.
Just some old machinist's tricks.
smile.gif


PS The very best drills I ever found for heavy work is the Guhring brand.These drills will work when all else fails.They are pricey though and still won't cut work hardened steel.
They are very accurate as to size too!!


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[This message has been edited by Yvsa (edited 01-12-2000).]
 
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