Cobalt drill bits in wood ?

[russ]

Does anyone know why there would be an issue of drilling wood with a Cobalt bit? Was reading an article and the author mentioned he wouldn't use Cobalt bits in wood.

Thanks for your input.

Russ

[sawduster]

I can't think of any. I think I've had some cobalt bits over the years and have used them for what ever needed drillin. Only thing I can think of is maybe the author felt that the cobalt bits were overkill for wood.

[TDHofstetter]

Overkill is the ticket - like VAST overkill. Cobalt bits are only very handy when you're drilling terribly hard steel or other metals that're really hard to drill, but possible to drill with HSS.

Here's whassup:

Carbon-steel drill bits are about as hard as steel drill bits get. They can overheat, though, drilling difficult materials without frequent cooldown pauses or lubrication. For most MOST purposes, carbon-steel drill bits are perfectly satisfactory... besides being cheaper than HSS.

To get around the overheating thing, HSS drill bits enter the picture. They're a lot harder to overheat, since they retain their hardness at a much (MUCH) higher temperature than carbon-steel drill bits do. HSS is generally overkill for drilling wood, exceptions being very deep holes or low feed rates.

Now... for situations involving VERY difficult-to-drill materials, it's possible to overheat even HSS to a temperature where it loses hardness. For those few situations, cobalt is added to the HSS to raise the annealing temperature even FURTHER. They're not harder, and they're not tougher, they just hold their hardness up into the glowing-yellow-hot temperature range. They're also slightly radioactive; I do own a couple of cobalt bits (bought for specific purposes), and I keep 'em in a special drawer where they can radiate with minimal impact on me.

[Leo Voisine]

Hey Russ,

Nothing at all wrong with cobalt drills. I use them all the time. I use carbide drills too. I also use drills with various different coatings.

All of that stuff is good.

Cobalt will stay sharper longer. It's kinda between HSS and Carbide.

I don't consider carbide on my saw blades overkill - and I don't consider cobalt drills to drill holes in wood overkill. I also don't consider carbide router bits over kill.

Many poeple have a stigma about tools. and what is overkill.

No cobalt is not "way" overkill. You don't necessarily "need" it. HSS will work just fine. I would not go out of my way to get the cobalt drills.

In drilling steels - often times Cobalt is better than carbide because it is not so brittle.

[sachbvn]

If you've got the cobalt bits - use em.... unless something like a forstner bit or a brad point bit would be more appropriate.

Your cobalt bits won't hurt anything, they are just a lot more expensive, so - while not "needed" for wood - there is no problem using them if you have them.


Zac