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Hollow chisel mortises vs Domino

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Hollow chisel mortises vs Domino

#1

Hollow chisel mortises vs Domino

Bill Tindall, E.Tn.


I recently made three tables where the legs were mortised into rails, conventional table construction. The mortises are shown in Picture 1. I bought a used Domino to evaluate it for this kind of task. The leg used two biscuits per rail, 4 mortises per leg. The rail was inset 1/8" from edge of leg face. A total of 32 mortises per table had to be cut. Four set-ups (fixing the fence on the machine in two dimensions, had to be made. This set-up was not quick. And each leg had to be secured before cutting. It was quick to cut the each mortise once the machine fences were set up. The location of the mortises was precise and there were no fitting problems of rails to legs.

The biscuits fit nicely into the end grain mortise of the rails. They did not into the flat grain of the legs. Most biscuits had to be diddled with to get an acceptable fit, that is, could be slid into place with hand pressure.

Had I cut the mortises with a chisel mortiser I could have cut one long mortise. Once the fence was set up on the mortise machine all the leg mortises could be cut with no further adjustment. The left and right handedness of the leg mortise could be dealt with by reversing the leg in the machine vice.

Making this table with the hollow chisel mortiser would have been much quicker, at least in my hands. Recall, I thought the Domino was faster for making case back frame and panels.

Re: Hollow chisel mortises vs Domino

#2

Re: Hollow chisel mortises vs Domino

Barry Irby

I too bought a used Domino and the systaner with the various Dominos and Bits. I have made about a dozen things with it, so I am by no means an expert, but I think it requires slightly different thinking than a hollow chisel mortiser. (Which I also have and have used a few dozen times.)

To do what you did, I would have set the spacing down from the surface once on the legs and then left it alone. Use the pins in the machine to sett eh distance from the top of the leg and top of the rail. To recess the leg without resetting the fence depth I keep a piece of 1/8" plexi scrap and just lay it on top of the rail under the fence. For the lower mortices, I would have lined up the top edge of the rail with the leg and drawn a line from one to the other or just used a adjustable square to give me a precise distance and marked them all and then used the bomb site one the Domino machine. In the case of the leg, looking through the plexi. I would have made all of the mortices on the narrow setting except the one on the leg where you are looking through the plexi. Than one would have been medium. The two mating ones near the top of the leg and rail would have registered the high of the rail even with the top of the leg.

I could have done a table in less time than it took to type this out.

As far as the fit of the dominos goes, I make my own and have had good luck with them fitting. On the purchased ones I have had to brush one of two on some 80 grit sandpaper to thin them down a bit. I suspect they shrink and swell with changes in humidity. They are embossed with some grooves and the name and that may have compressed them. I wonder if the intention was to let them slide into the joint and then swell a few thousandths from the water in the glue? Also, I think the bit cuts differently in end grain vs. side grain.

I have about a thousand 16" long birch or maple sticks 3/8 thick, 7/8 wide with round edges. Unfortunately the 10mm cutter is about .02" too big so I reduced the stripos to 8mm and them cut them to 40 and 50 mm long. It very slowly dawned on me that I could make even thinner ones. Make your own out of scraps or if you wish I can send you some of my sticks to make some out of. I am such a cheapskate I would rather waste an hour making them than pay for any. Some people on the Festool Forum claim home made ones are stronger.

Re: Hollow chisel mortises vs Domino

#3

Designing a table to fit the Donmino

Bill Tindall, E.Tn.

Designing a table to fit the Domino? Not the way I work.

"I would have set the spacing down from the surface once on the legs and then left it alone". did that

"Use the pins in the machine to set the distance from the top of the leg and top of the rail." Think about this claim. What you suggest only works if the rail height accommodates using the pin spacing. In my case it did not. The pin located the top mortise to where there was no room for a second lower mortise.

"To recess the leg without resetting the fence" did that too

"For the lower mortises, I would have used the bomb site." These are relatively

long legs on a dainty rail. This M&T joint needs to be as strong as possible. Oversizing the vertical distance on the mortise means the joint strength relies on glue. Ideally the joint strength should rely on the strength of the wood with the glue just holding the wood together. It was the inability of to use the pin spacer and the need to get this lower mortise perfect that made making the joints with the Domino much more time consuming than by hollow chisel mortise.

This project illustrates a limitation of the Domino. It has features that make using it efficient. But these features limit application. In this case I needed a mortise longer than one biscuit. That required two biscuits and that in turn required locating the mortises to great accuracy. Second, features for repetitive mortise location may not accommodate where mortises need to be made. For the case at hand the features of a hollow chisel mortiser were superior for productivity.

Re: Hollow chisel mortises vs Domino

#4

Re: Designing a table to fit the Donmino

Barry Irby

I have little doubt that well made traditional mortise and tenon joints are stronger than Dominoes. How much is the question.

As far as positioning the dominoes, just make the marks for both sets and cut them. Or Festool has a bar that can be mounted on the machine to accurately position them in positions other than the built in stop. (Vaguely like a cross slide vice.

This is no more complicated than using the traditional method. Just different. If you were not experienced with a hollow chisel mortiser it would be simple. Both are easy, just not the same.

As an aside, I believe the strength of either of these joints is based on how difficult it is to extract the tenon from the mortise. Assuming the tenon is sound and does not break.