Piano legs joint

[Tom Spallone]

I have been commissioned to make legs for a special type of piano. The Piano restoration place that has me doing this job has very specific requirements as one can imagine. The legs themselves attach to a 1 5/8" thick "plate" which is then bolted to the underside of the piano.

They wanted me to create a "natural" dowel out of the top end of the leg. Meaning, sort of "turned" to make a 1 1/2" dowel at the top of the leg which will pass through an opening in the plate. He definately didn't want a seperate 1 1/2" dowel piece inserted in the end of the leg and then have the dowel inserted into the plate. This was for structural purposes.

Well, I don't have a lathe but I managed pretty well. The question is; he then wants me to cut a wedge of sorts into the top of the "dowel" and then hammer in another piece of hardwood to sort of spread out the "dowel" so that the glued up joint will be rock solid.

Sounds great. But, MY question is, how big of a wedge, how deep, that sort of thing? I don't want the thing to split. Then I'd be sunk. I tried to give pictures but couldn't manage to attach them.

Any suggestions?

[Larry Reimer]

Tom, I would drill a hole through the "dowel" at the bottom of the wedge and lined up with the wedge. That would help keep the "dowel" from splitting from driving the wedge. Can't help you much with the size of the wedge, I think that would depend on how tight the joint fits and what kind of wood. The tighter the joint fits and the harder the wood the thinner the wedge.

So, how did you make the "dowel" without the use of a lathe?

[Ted Jay]

...

Sounds great. But, MY question is, how big of a wedge, how deep, that sort of thing? I don't want the thing to split. Then I'd be sunk. I tried to give pictures but couldn't manage to attach them.

Any suggestions?

How far out of the top is the dowel sticking out, and how much clearance? It shouldn't be much either way, a snug fit I imagine. If you cut a kerf and hammered in a wedge and with a tight fit it shouldn't spread out that much to split it, just make it snug. All your doing is making it "snugger" (a new word) in an already snug hole, right?
I just can't remember if you cut the kerf with or across the grain, I think its with the grain???
I hope that helps.
Ted

[Tom Spallone]

Yes, you're right that I am just making it "snugger". And the other suggestion about drilling a hole through the dowel puts my worries at ease to avoid "splittage"

Thanks. I see there's a certain amount of common sense.

[Cliff Rohrabacher]

Yah the thinner the better especially since all you want is to tighten the interface. The cut can be a back-saw kerf the wedge ought to be a really gentle taper so as to get the most insertion possible. If the "dowel" must not turn - ever - and there will be stresses that tend to induce turning you might also consider a dutchman down the side of the dowel and the hole.

[Alan Turner]

Tom,
From what you say, the wedge will be blind once the plate is installed. I think I would do two wedges, cut at about 3 degrees. The shots should be close enough to the two edges so that you can acutally move the tenon. On a sgtraight tenon, this is usually about 1/4" or so, but with a round tenon, 3/8" or so might b e better.

The wedges should be installed cross grain to the plate (assuming that the plate is of wood). This way, you will not be trying to split the plate when you drive the wedges. You will be driving it into the endgain of the plate. You might consider making the holes slighly tapered with a rat tail file to accomodate the dovetailing effect of driving the wedges. Fill the slot with glue; none on the wedge, before driving. This way the wedge will not expand with the moisture from the glue before you seat it.

So, how did you make the tenon round? Carve it?

[Tom Spallone]

I marked the top with the inside of a toilet paper tube. Cut the most of the material with a table saw, filed, belt sander, hand sanding.