Tips for domino angled mortises?

[Kenneth Walton]

Hi guys,

I'm going to be building a set of chairs soon. I've built a Morris chair and a sculpted rocker, and was able to work around the various angles. These chairs are going to be standard dining chairs, with about a 5 degree slant backwards and a few degrees from front to back in width.

I'd like to use my domino for the joinery. I can work out how to make all the parts and various angles. My issue is locating the mortises on the angled ends to have the appropriate setback.

When I made a coopered seat, I used dominos for alignment. The problem was when you change the angle of the fence, you change the distance from the fence to the center of the mortise. This screwed up the up-down position of the mortise slightly, and made the edges not line up the way I thought they would.

Anyone have any tips or tricks for angled mortises with the domino? Or helpful hints for building chairs with the domino before I destroy too much walnut? Thanks!

Ken

[Mike Henderson]

When I've made chairs, I always cut the back legs/seat back so that the part facing the seat rails was straight up and down. Then you only have to deal with the angle of the seat rail into the back. I've never used the Domino for those joints but I would think that cutting the mortise so that the domino goes straight into the back would be fairly straightforward.

I'd probably take some scrap of the same thickness as the seat side rails and make a trial cut or two.

Mike

[When you look at a chair, the back legs usually angle backwards, and the seat back usually angles backward. So the piece of wood that you cut is shaped sort of like the letter "C". Make sure to save the face of the original board for the joint to the seat.]

P.S. Normally you put a chair together by gluing up the back and the front as independent units. Then put the front and back together. Having the tenons go straight into the back legs makes the assembly easier.

[Prashun Patel]

I know exactly what you mean. I found out the hard way.

You can use shims to create a 90 degree reference surface if you work off the convex side of the curve.

On a Maloof seat cooper, where the center two joints cup upward, you'd reference your Domino off the bottom. For the flanking outer joints that are convex as viewed from above, you'd reference off the top faces. In both cases, you use your 5 degree shim to support the fence allowing you to come in at 90 degrees to each face.

Now that I think about it, if you coopered the same angle on all your boards (so instead of just doing 2 and 4 at 5 degrees, you could do them all at 2.5 degrees, then it might be irrelevant what the offset for the fence is, since they'd all be offset by the same amount.

[Kenneth Walton]

Prashun, I think that's what I'll do next time I make a Maloof seat! It ended up being not a big deal to scrape and sand to level, I'm just looking ahead to where I might get slight misalignment in a normal dining room chair and the seat looking weird.

Thanks for the tips Mike, I'll keep them in mind. Especially saving the offcuts!