dovetailed peg holes

[DJ Delorie]

I'm designing a project that is calling for a dovetailed peg, but I can't figure out how to drill the hole. By "dovetail peg" think "wooden nail" except the head is tapered intead of just flat. A turned dowel would be pushed through the hole, and the taper would provide a big bearing surface. Picture:

| | | | | |

--------| |-------- / \ / \

-----/_________\-----

In my case, I want the angle to be more like 10-15 degrees, and the thin end of the dowel to be about 1/2". The board is 3/4" thick.

Grizzly has a 15 degree bowl edge bit that would work except that the bearing is 5/8" - a bit too big. A dovetail bit small enough to fit through the 1/2" hole wouldn't reach across the 3/4" board.

The board is too big for the lathe or scroll saw, and a jig saw isn't accurate enough.

Ideas?

If I can't figure this out, I'll try a stepped hole. Anyone have info on the comparative strengths of this vs the dovetail I describe above?

Thanks, DJ

[bridgerfafc]

10 to 15 degrees seems a bit shallow to give a positive seat, but a positive seat may not be what you're after. if the taper providing a big bearing surface means the peg is rotating I think that the taper is going to give you problems with binding and jamming.

countersink bit?

the stepped hole would probably be stronger. look up "counterbore"

[DJ Delorie]

It's for a set of shelves; that peg holds the shelf up, as if the shelf were hanging from the one above it (the peg is glued into a hole in the turning above it). So, no rotating, it will all be glued together. The physics of it all should be similar to how normal dovetails work.

[StephenM]

How about not making the end not a dovetail, but instat a single step like this:

--- ---------------------- | | - - | |

--------------------------- It's easier to execute and looks exactly the same after assembly.

\Steve

[Garage_Woodworks]

Countersink

[dadiOH]

are numerous others that would too but you'd have to put it through the hole and then chuck it, position for height then turn on router and us bit shank to guide on hole. For that matter, is there any particular reason to bevel the hole through the entire thickness of the 3/4" board? If not, you have many bits from which to choose.

[J. Clarke]

If it's just one or two I'd whittle it out with a die grinder (or Dremel) or an X-Acto knife. If you've got a bunch of them and can't find a suitable countersink or router bit then get a spade bit of the appropriate diameter and grind it to the right profile.

[Leuf]

There are "tapered end mills" but usually once you get up to 1/2" diam hole there is only a couple degrees of taper.

There are also vertical panel raising bits that are similar to the bowl bit you mentioned but they don't have a bearing at the end. I think the small diameter is close to 5/8" still though.

And final idea, since you are making the pegs yourself, who says it has to be a straight taper? You could use something like a 3/4" radius plunge roundover and not plunge it full depth.

-Leuf

[DJ Delorie]

Those are 41 degrees; I wanted 10-15 degrees.

[DJ Delorie]

Before I route the bevel, the hole is 1/2" diameter all the way through, so the bit has to fit in that size hole. If it did, I could put it through after chucking it. The largest bits that are 1/2" diameter are:

8 deg 13/16" tall 10 deg 5/8" tall 14 deg 1/2" tall

I might be able to use the 10 degree one; that makes the radius 1/8" bigger on the bottom (3/4 diam "head").

Strength. I'll probably not go *all* the way through, just to avoid making the exit hole any bigger. But, it's the side grain in the dovetail peg that's doing the heavy lifting; the more of that I have, the more it should hold.

[else24]

Here's a thought if all else fails. :-)

[whit3rd]

It's possible to use a sliding dovetail slot, with a slat, to do the same kind of shelf-holdup. That's something I've done.

Your stepped hole idea is much easier to make accurately, because the wood dowel can wedge its way tighter in the hole, and the shelf will slip down. The stepped hole and the dovetail dowel both suffer from short-grain weakness... the larger contact area of a sliding dovetail gets around that problem.

[Gerald Ross]

What holds the peg above? Will it be dovetailed or just straight and glued?

[Gerald Ross]

If the end doesn't show, I would make a tapered hole, use a straight dowel split the end and drive in a wedge.

[DJ Delorie]

It's straight, glued into a drilled hole in the bottom of another turning.

[DJ Delorie]

It shows. Yes, I thought of that idea too :-)

[Fred the Red Shirt]

:-)

that was the first tool that came to my mind.

[Fred the Red Shirt]

Dovetailed it at both ends would be a neat trick...

Actually he could use straight dowels split and wedged at both ends.

[DJ Delorie]

[StephenM]

Build a test case.. I'll bet you can stand on it.