Pilotless counterbore

[Jon Slaughter]

I'm in need of making about a 5/16 counter bore into hard wood only about

1/16th deep. Exact measurements are not needed but it should be fairly flat with no pilot hole(or something that is no more than 1/32nd deep).

I can use a press and again, position and hole size are not that important. Basically I am trying to create space so that some woot can fit flush with, say, a screw head, but the wood is only about 1/8 thick(so any pilot holes may go completely through).

Actually I would like for the holes to be square or rectangle(as I have some other objects I need to cut "slots" in the board that do not go all the way through.

Accuracy is not important except for depth since I cannot go through the board and I would like it to be relatively nice looking cuts. Circular bores have to be oversized because the things I am using are actually square or rectangular.

I'm not a woodworker so I don't know how this is would generally be done(I imagine it would be extremely easy with a cnc). Obviously one can use a chisel but I'm not proficient enough to make it look decent and probably will screw up the wood.

I've seen forstner bits and counterbore bits but they all seem to have create pilot hole.

[Artemus]

You could just grind the center nib off of a forstner bit. That would pretty much require you to use it in a drill press but you said you had one. Another option would be a CNC router. Given the thinness of your material you may also want to consider a vacuum hold down to keep it flat to the table while drilling/machining Art

[dpb]

There are centerless Forstners. (The spur is no deeper than the rim so they make flat-bottom hole)

[routerman]

Slo-down spiral 5/16 x 1/2 shank 2 flute solid carbide router bit will do it.

***************************************************************************= ** I'm in need of making about a 5/16 counter bore into hard wood only about

[Upscale]

On Sat, 23 Jan 2010 14:37:41 -0600, "Jon Slaughter"

The most important part of the the cuttin you need to make is the outside edges on your project surface. To that end, I'd suggest cutting a through template (using a piece of sheet plastic or something like that) in something else the exact size of the item you want to insert. Once you have that cut to size and to your satisfaction, then you clamp it to your actual project surface and use that template with a razor knive or similar to cut the surface of your actual project. If you screw up the initial cutting of the template, it's a small loss and not affecting the actual project surface.

Assuming you don't cut the inside edges of the template, whatever lines you do cut will be on the inside edges of your project and relatively unimportant. You'd cut until you're satisfied with the indent you want to create.

[whit3rd]

This is a lot like making a hinge mortise, can be done in the same way. A small (Dremel tool) router and some kind of guide is one approach. Either a Forstner drill (makes flat-bottom holes) or a machinist's end mill (not perfect for wood, but easily available) can do the round-hole case. Some hand-chisel work is easily done to clean up the corners.

A common way to sink iron a small distance in wood, is to heat it red hot and press in to burn a socket. Practice on scraps, of course, and keep a water bucket handy.

[Jon Slaughter]

My father mentioned something like this. How well does it actually work? I figured it wouldn't do much more than char the wood.

I'm going to run to the hardware store and see what kinda bits they have. But if I can use the heat method and get about 1mm to 2mm penetration without it destroying the wood then it would probably work out very well for most of the things I need to do.

[whit3rd]

I've only used the method for coarse work (like attaching handles); it has the capacity to darken oak or maple wood, but if you get the tool hot enough, a second's application won't penetrate even thin workpieces. Sign shops often char the wood, then clean up the black bits with a little sandblasting. A fine wire brush would be useful, I suspect.