Forstner Bits

[Keith nuttle]

I recently did a small project that required multiple hole that I drilled with a Forstner Bit. The holes were about a half inch in diameter and about and inch deep.

Until this project I would use the Forstner Bit to recess bolts and other simple projects that required on or two shallow holes.

I had a lot of trouble with heat. After I noticed there was a burning problem, I was very carefully to control the feed rate but this did not seem to resolve the problem.

Is this problem cause by my poor techniques or would better bits solve the problem.

[skeez]

slow down the speed of the drill press. forstners like slow speeds.

skeez

[Leon]

Typically these bits should be run in the 400 RPM or slower range. How fast were you drilling? Did you lift the bit to clear the chips often?

[Kenneth]

I wonder how many holes were being drilled... (and what material was being drilled.)

It sounds like it might just be a dull bit.

All the best,

[Kenneth]

I should have added that I agree completely with the slow speed issue...

All the best,

[Leon]

Entirely possible but I have a 1-3/8" Forstner bit that I have literally drilled hundreds of holes with in hard woods and MDF for probably 10 or 12 complete kitchen hinge jobs and the bit still cuts respectably. Then again there are many different qualities of bits.

[Kenneth]

Hello again,

The quality differences I have seen with some of my Forstners is amazing.

I have some cheapos that are about shot after very few uses. Others, clearly of much higher quality seem to last forever.

Somehow, more than with other types of bits, it seems you get what you pay for.

All the best,

[Lew Hodgett]

After carbide, it's all down hill.

Lew

[name]

Keith nuttle skreiv:

Fine Woodworking recently did a test of a bunch of forstner bits. You might want to have a look at that. They found significant variation in heat build up between brands.

[J. Clarke]

Here are a couple of tables of speeds for Forstner bits

that they differ somewhat on speeds. Note also that they agree that one should use lower speeds on "hardwoods" than on "softwoods".

Yours may have come with a table of recommended speeds--if it did then follow that unless you get burning at the recommended speeds, if so then reduce the RPM until you don't anymore and make a note of the speed.

Carbon steel Forstners you can ruin easily with excessive speed--examine the bits for any blue discoloration and if you find it then the bit is shot.

Also make sure the bit is sharp--steel Forstners are actually pretty easy to sharpen if you have one of these

(I keep it in my wallet, it's handy when the Swiss Army Knife decides it doesn't want to cut).

[Kenneth]

Hi Keith,

A set of really high quality Forstners will set you back a fortune...

But, as I mentioned earlier in the thread, the differences in quality will make a significant difference.

You might consider buying 'em individually as you need a particular size. Over time, you would assemble a high quality set without having to sell your home.

All the best,

[Keith nuttle]

I guess the answer to my question is both my technique and drill bits. I set the drill up for standard twist drills and used that speed, so it was probably much faster than it should have been The next time I need to slow it down quit a bit. (I don't remember the exact speed since I have had the drill press for sometime and have not changed it since I got it. )

As I said I don't use the Forstner often, so had picked up a quite cheap set to see what they would do and learn to use them. I will have to get a better set before I start a real project.

I was drilling a piece of clear soft pine.

I will read up on the use of the Forstner bits

[Leon]

Agreed, keep the cheap set and when you dull a bit replace it with a quality bit. No since in buying new ones till you need them.

[Father Haskell]

Dull bit or poor relief. Something's rubbing, probably the sides of the bit or the undersides of the lifters. Sharpening is possible (file or slip, do NOT file the outside of the bit or the undersides of the lifters), but a pain. Replacement is best. Freuds are cheap and work well. Brad points might work better for your application.

[else24]

My last project required over a hundred 3/8 holes a half inch deep. I went with a brad point bit. They last longer and it's easier to hit the target.

That said, I had a bunch of 3/4 holes to drill a while back and all I had was a cheap set of forstners my sister gave me for Christmas. The

3/4 bit burned up after ten holes and I had it on slow speed and feed. I'm pretty sure the bit I bought at Woodcraft cost as much as that whole BigBox set but it cut many dozens of holes clean and fast with no burn and it's still cutting.

Now I have a set of cheap forstners with two expensive ones in the set. (I, uh, dropped one and chipped it...) The others have done fine for what I've had to do. When I need a better one for a specific job, I'll go get it.

[Father Haskell]

Stanley Powerbores were great, cheap, *easy* to resharpen with a triangular file, and cut smooth, crisp holes in no time flat.

to find a set locally, short of the flea market. Stanley quit making them. It's either pay $60 for what used to sell for about $20 per set, or hire a machinist.

[Kenneth]

Howdy,

Those might be great for certain purposes, but there are things that Forstners can do that would not be possible with the Powerbores.

All the best,

[Father Haskell]

Half and pocket holes come to mind. Forstners don't take abuse well, and like I said, Powerbores are a LOT easier to sharpen when you blunt the edges. You wouldn't use a Norris A-1 to plane a door slab, would you?