Domino Z Chair

[rlatshaw]

Here's my version of the Domino Z Chair, built using David's most excellent instructions in Woodcraft Magazine. (Thanks David.) The chair is constructed of 30 year old hard maple, left over from building my work bench. (Yes, it took me almost 30 years to finish the bench -another story.) Here's a shot of the chair in the clamps:

[attachthumb=1]

I followed David's construction suggestions except for the following:

1. I used Titebond III to glue up the joints and Dominos. All seem to be holding just fine. (I did use epoxy to set the brass screws.)

2. In a previous life, I twisted the head off of a brass screw while attempting to drive it into hard maple. Consequently, I drilled the pilot holes with a #23 drill bit, which is a few thou smaller than a #8 screw shank.

Here is the completed chair, finished with four coats of Waterlox Original Sealer/Finish and rubbed out with 0000 steel wool and Johnson's paste wax.

[attachthumb=2]

[attachthumb=3]

 

[Rocker]

Looking good, Dick. I must admit I am dubious about using a PVA glue for the miter joints, owing to its tendency to creep, and to soak into end-grain, starving the joint of glue. But probably the brass screws will keep you out of trouble.

David

 

[markcoutinho]

Finally I started to build a trial-version of this chair. But I've bumped into a problem which I can't solve and it's about Domino'ing the thing.
It's especially about the 22,5 degrees joints. How on earth does one get the Domino-holes as showed in David's manual? If the hole would be from left to right instead of this one (which is in my view from up to down - sorry for this poor English) I can figure it out, but that's not as strong as it's supposed to be.
Do I have to use one of the stops and put them against the end of the piece of wood?

Phew... Hope you all understand my question. Thanks in advance for helping me out!

 

[Zaphod]

I've been tinkering with a version of the chair as well.  A few observations:

I made a few test joints similar to David's with the exception of two 8mm dominoes at the inside of the 22.5 miters.  I  used system3's T88 structural epoxy and Titebond3
Let both cure for a few days and tested strength by trying to break the joint with a K-body clamp to no avail.  I then employed my precisely calibrated sledge hammer.  Both joints were amazingly strong with no clear winner.

The brass pins are a nice aesthetic touch but provide little, if any, structural strength.

 

[Rocker]

Mark,

I am not sure that I have understood your question, but these two pictures show the joint glue-up. The joint is initially glued together with just a single domino for alignment as shown in the first pic, using System 3 epoxy and 22.5 degree wedges with sandpaper glued on to facilitate clamping. The single domino is set in the mortises milled in the faces of the miter joint as your picture shows. When the epoxy has set, the squeeze-out is cleaned up before milling the three mortises for the locking dominoes, as shown in the second pic.

I agree with Zaphod that the brass pins don't add significantly to the strength of the joint, and may even weaken it.

Another possible method of reinforcing the joint is to cut a pair of 3" deep kerfs by clamping the glued-up joint joint apex-down to a tablesaw tenoning jig, and glueing in two 1/8" thick splines instead of the locking dominoes; see picture 3. I have tested a chair frame made by this method to destruction. The joints ultimately failed under a load of 800 lbs.

Rocker

 

[nickao]

I have seen this type chair in magazines before and have always loved it.

This is a nice little project that takes much more skill than it appears. Nice explanation and pictures  Rocker. Nice Festool application of the Domino in action!

Another in contention for this month?

Comments?

Let's get some feedback on these projects or I can only vote on what I think. I may be missing some key points I know the guys on this forum can point out.

This is the 3rd project I have picked for a running in the contest.

Nickao

 

[markcoutinho]

Thanks for your reply, Rocker.
But the one thing I'm curious about is: how do I get this initial Domino on the place where it's supposed to be? Should I use the pin and put that against the very edge of the 22,5 degrees? If yes: this very edge is too weak - the pin goes through it a bit. Or shouldn't I be bothered with that too much?

 

[Rocker]

Mark,

I did not use the index pins for any of the dominoes in the miter joint. Just make a pencil mark, as you would for a biscuit; but you need to clamp a backing cleat level with the workpiece to ensure that the Domino's fence has a sufficient area to rest on, so that the mortise is milled exactly perpendicular to the miter face.

Rocker

 

[markcoutinho]

Ah, that's clear, Rocker. I'll give it a go. Thanks!