Forstner Bits without Brad Point?

Question

I'm trying to drill holes most of the way through a block of wood to mount magnets which will be attracting metal through the solid face of the wood.

Because of how quickly magnetic attraction falls off, I want to leave a minimum of wood (less than 1/8"). I'm using forstner Bits with a drill press today, but my issue is that the Brad Point is long enough that without puncturing the face of the wood the magnets produce insufficient pull.

Since forstner Bits are edge guided, it seems like the brad point is unnecessary except for lining up where the hole goes. Are there versions of a forstner bit that don't have the brad point? If not, would I create a problem for myself if I ground off the tip on my bit?

Possible duplicate of How to make a 3/4" flat bottomed hole? Also related, https://woodworking.stackexchange.com/questions/4904/ and https://woodworking.stackexchange.com/questions/7923/ — Graphus, Oct 05 '19 at 07:02
I'd only note that my specific question relates to the availability of a variant drill bit and modification of a drill bit. — Mark, Oct 05 '19 at 11:42

score 5 · Accepted Answer · answered Oct 04 '19 at 16:03

If you grind off the tip you'll want to use a guide block to make sure the bit doesn't wander when you're starting the hole.

To make a guide block just drill a hole the same size through another piece of wood and line it up with where you want your hole to be. Clamp it to the work piece and your drill bit won't wander.

This is also useful if you want to drill a larger hole accurately at an angle. Just make your guide block straight in a larger piece of wood and then cut it to the appropriate angle.

The only other issue with not having a tip is that the material won't be cleared from the center of the hole. This might require a pilot hole or increased feed pressure.

score 2 · Answer 2 · answered Oct 04 '19 at 15:28

A "typical" design for forstner bits is one where the brad point is no deeper than (and often even with) the cutting edges, which means they are suitable for creating flat-bottom holes or insets. That is, the point on many traditional forstner bits should be no longer than the cutting edges.

Removing the point will cause it to wander unless you are really careful. Even in a drill press I suspect it would oval out a little, but I suppose this depends on the total tooling setup.

So, find bits that are designed to make flat-bottom holes and you should be ok if you are careful with your depth of cut.

Alternatively, you could cut the holes with a plunge router and a suitable bit. This might be overkill, but it is often how euro-style cabinets are machined to accept those inset round hinges. Though, this is usually done in a factory. In a home shop, a sharp forstner bit at the right speed and feed should do well.

Forstner Bits without Brad Point?

2 Answers2