Domino question

[scott vroom]

Hi, I'm building a cabinet with 1.75" square face frame members and two 8 x 50mm dominoes at each joint oriented to optimize resistance to racking. The mortises at the stile will be 8mm so no wiggle room. The mortises in the rails will be 14mm and I prefer not having the 6mm slop running in the racking direction. The attached rendering (no where near scale) shows how I want to orient the dominoes on the stiles. The challenge is using a dead-on accurate reference for the mortises on the rail that keeps both ends of the stile perfectly square to the rails. Any tricks you could share?

The easy method would be to rotate the dominoes 90 degrees...and maybe I shouldn't be concerned with racking.

[Kevin Jenness]

Your drawing shows that the domino face grain would be glued to end grain in the long member. The joints would be stronger and easier to index with the dominos turned 90*. I would stack the dominos and index off a center mark. My 500 fence will adjust in height up to 40mm, so you could work from both faces depending how deep you want the second domino. That requires the stock to be consistent in thickness. Otherwise, work off the base and use a shim for the offset. The second method would work for the orientation as drawn.

For a stronger joint (if desired) you could make overlapping mortises and use wider splines.

[Randy Heinemann]

With a solidly glued Domino, I can't imagine racking would be an issue, especially with 8mm Dominos. Generally I would probably use a 6mm Domino. Unless this cabinet is meant to withstand a lot of abuse and hold really heavy items, there should be no problems. Just make sure that there is sufficient glue to be sure the Domino is covered well when sliding it in the slot. I have never had any Domino joint fail and don't expect to. I would also say that rotating the Dominos 90 degrees, so the width of the Domino is parallel to the grain of the top and bottom parts, is a good idea.

[scott vroom]

The project is a 68 x 23 vanity cab, inset doors/drawers. with a 1" solid wood top + sink. All that load will transfer to four legs tapered to 1.25" sitting on a tile floor that is not perfectly flat. Any un-eveness in the floor will make the cab want to torque. The cab rear will have top and bottom stretchers but there is little lateral structural support in the front frame. The stiles will be in compression so not too worried about the domino faces running cross grain. I plan to make the mortises wider on one of the pieces to allow for adjustment. I have little experience with dominoes so I don't know the potential for glue joints to fail in the wider mortises allowing the tenon to go off center. It's probably low risk. Thanks for your inputs.

[Michael Burnside]

At the end of the day, you want as much long-grain-to-long-grain adhesion as possible. THIS is what makes the tenon strong. Really the frame you have will need reinforcement in the overall carcass design to prevent racking, even if you made these tenons by hand. I see no point over-designing only one part of the design. At least that's my opinion.

As a side note, I rarely do anything but tight setting on my domino. This is particularly true when I feel the tenon is providing additional long-grain adhesion or twisting/shifting strength. I recommend you do the same and if you find you have a slight fitment issue, it's easy to trim down the domino with a razor blade to get an exact fit.

This is, of course, predicated on the fact that you measure/mark and accurately mill the mortise.

[Kevin Jenness]

You gain nothing by using the wider setting but compensation for sloppy layout and milling, and you lose the inherent racking resistance of a well-glued tight fitting joint. If you dry clamp the parts in place and strike index marks across the joints with a sharp pencil, then mill the mortises with the machine center mark aligned with the pencil marks, the joints should go together as designed. As Michael said, you can trim the spines on the domino edges if necessary.

Crossgrain mortises at the center stile-rail joints will weaken them just where you want the combined beam strength of the rails to prevent the bottom deck from sagging on this wide cabinet. My $.02.

[Michael Burnside]

You gain nothing by using the wider setting but compensation for sloppy layout and milling, and you lose the inherent racking resistance of a well-glued tight fitting joint. If you dry clamp the parts in place and strike index marks across the joints with a sharp pencil, then mill the mortises with the machine center mark aligned with the pencil marks, the joints should go together as designed. As Michael said, you can trim the spines on the domino edges if necessary.

Crossgrain mortises at the center stile-rail joints will weaken them just where you want the combined beam strength of the rails to prevent the bottom deck from sagging on this wide cabinet. My $.02.

I agree with this comment, 100%

[Jim Becker]

The wider cutting option with the Domino machines is handy for when you are using the tenons primarily for vertical alignment...a bunch of them...and you want/need to be able to get say, a panel, glued and clamped in a reasonable amount of time. I would not select that option for actually joinery like you describe. Take care in cutting the mortises accurately and there's no real need for any slop at all. You can always Lightly abrade the edges of a Domino tenon if it's a hair too tight so you can get things together. I'll also suggest you keep a set of Domino tenons that are already slightly sanded to be used for dry fit...dye them a noticeable color. That way you can check the fit and still get things apart without damage and do the final glue up with pristine Domino tenons for a very tight joint. (It would be no different with traditional mortises and loose tenons in the same situations)

[scott vroom]

The wider cutting option with the Domino machines is handy for when you are using the tenons primarily for vertical alignment...a bunch of them...and you want/need to be able to get say, a panel, glued and clamped in a reasonable amount of time. I would not select that option for actually joinery like you describe. Take care in cutting the mortises accurately and there's no real need for any slop at all. You can always Lightly abrade the edges of a Domino tenon if it's a hair too tight so you can get things together. I'll also suggest you keep a set of Domino tenons that are already slightly sanded to be used for dry fit...dye them a noticeable color. That way you can check the fit and still get things apart without damage and do the final glue up with pristine Domino tenons for a very tight joint.

OK, ok, you guys have guilted me into losing the slop in the mortises and orienting the tenon faces for long grain adhesion. Good tip on dry clamping and striking the index line across both pieces. Thanks for all of the inputs, really helpful.

Jim, the only other time I used the Domino was on a dresser. To align the finished end panels to the front and rear legs I used small 4mm or 5mm tenons for alignment, maybe 5 or 6 per side. And I made the mistake of drilling ALL the mortises extra wide. Absolute chaos with tenons sliding every which way, both sides of the panel. Somehow I managed to get it clamped up. Lesson learned.

[Michael Burnside]

One trick on panel glue ups when using the loose setting is to pick one end, using a tab on the domino, and make both boards tight. Then do the rest loose. This will make easy alignment and the one tight domino will prevent sliding back and forth.

[Kevin Jenness]

One trick on panel glue ups when using the loose setting is to pick one end, using a tab on the domino, and make both boards tight. Then do the rest loose. This will make easy alignment and the one tight domino will prevent sliding back and forth.

A version of that is to make tight mortises all along one piece and at the initial point on the other. The dominos in the tight mortised piece will drive in square and stay located on centerwhile they easily find their way into the wide mortises.

You can ease entry into tight mortises by putting a slight bevel on the leading end of the dominos.

[Jared Sankovich]

You gain nothing by using the wider setting

My $.02.

Unless you are using domino's that are the width of the wide setting.

[Jim Becker]

Jim, the only other time I used the Domino was on a dresser. To align the finished end panels to the front and rear legs I used small 4mm or 5mm tenons for alignment, maybe 5 or 6 per side. And I made the mistake of drilling ALL the mortises extra wide. Absolute chaos with tenons sliding every which way, both sides of the panel. Somehow I managed to get it clamped up. Lesson learned.

Yea...it's a "best practice" to leave one, in the middle for me, at the tight setting for a panel glue up as it keeps things from sliding while the others being loser laterally allow bringing things together more easily. Domino tenons, by their nature, are "quite snug" and a whole bunch of them needing to insert at the same time can be a "gorilla level task". And, as you mention, all lose can make things very sloppy laterally.

[Michael Burnside]

Unless you are using domino's that are the width of the wide setting.

I don't quite understand this statement, can you clarify? I'm interpreting this as you make a wide slot but you custom make a domino the width of that slot. Is that tenon not then tight and therefore emphasizing Kevin's point? I guess I've never found the need for a custom wide domino where two tight wouldn't work, but perhaps there is a situation I've not yet encountered?

[Jared Sankovich]

I don't quite understand this statement, can you clarify? I'm interpreting this as you make a wide slot but you custom make a domino the width of that slot. Is that tenon not then tight and therefore emphasizing Kevin's point? I guess I've never found the need for a custom wide domino where two tight wouldn't work, but perhaps there is a situation I've not yet encountered?

Yes, it's the same as the using the tight setting except you gain a larger glue surface. I've never used the narrow setting in all the years I've had a domino. I just make the width match the wide setting. I've also never purchased domino's.