Biscuit vs. Domino Joinery

[Steve Mathews]

In an Ishitani video it shows him using 2 rows of biscuits to join some wood slabs together for a table top. In a Rob Cosman video he explains that 2 rows of splines were used to join the pieces to his workbench top. I've also seen where the Domino system is used for this purpose. As a novice woodworker I haven't used either methods yet but would like to know which one is better and why. Anyone?

[Prashun Patel]

To join edges of a workbench or slab top, those guys are only using dominos, splines, and biscuits to help align the joint. The majority of the holding power will come from a properly jointed and glued edge.

It doesn’t matter too much which you use.

The choice of floating tenon would be more critical if one of the edges were end grain.

[Andrew Hughes]

I think every little bit of long grain that’s taken away reduce the chance of having a very strong glue joint.
Some are will to trade that for aligning the tops of the boards.
What side will you take.

[Steve Mathews]

I think every little bit of long grain that’s taken away reduce the chance of having a very strong glue joint.
Some are will to trade that for aligning the tops of the boards.
What side will you take.

Cosman mentioned that the double spline he used to align/join his workbench top was somewhat problematic. Some of the glue between the splines became trapped and prevented some of boards from joining properly. Makes sense.

So, as far as joining boards together the least amount of space taken up on long grain by a biscuit or tenon while providing alignment is better?

[Jim Becker]

Using too many fasteners might take away from the strength of the glue joint, but the few that are "typically" used by folks for alignment, etc., are not going to materially be an issue, IMHO. I use Dominos, although I still have a biscuit joiner, because I happen to love the system. In addition to the alignment they honestly help me as a solitary woodworker to get something together assembled and glued up. 'Kinda like a few small extra hands. Regardless of the fastener type, the single rule is always to index from the same surface point on all pieces. IE, the top on a table is common. Any minor variation in thickness between boards is then on the bottom/other side from the surface you've indexed from. Dominos, dowels, biscuits, splines, whatever...that rule works.

[Steve Mathews]

Using too many fasteners might take away from the strength of the glue joint, but the few that are "typically" used by folks for alignment, etc., are not going to materially be an issue, IMHO. I use Dominos, although I still have a biscuit joiner, because I happen to love the system. In addition to the alignment they honestly help me as a solitary woodworker to get something together assembled and glued up. 'Kinda like a few small extra hands. Regardless of the fastener type, the single rule is always to index from the same surface point on all pieces. IE, the top on a table is common. Any minor variation in thickness between boards is then on the bottom/other side from the surface you've indexed from. Dominos, dowels, biscuits, splines, whatever...that rule works.

If you don't mind me asking what is it about the Domino system that you enjoy?

[Jim Becker]

I like the precise fit of the system, the variety of Domino sizes that can be sized to be appropriate for the intended joinery, the ease of use, the excellent dust collection and so forth. I happen to use the larger 700 XL because most of my use is larger things like doors and big furniture things, but I have the Seneca adapter that lets me use even the tiny 4mm Dominos. 10mm, 12mm and 14mm get the most action in my projects so that's why I chose the larger one for my work. I've also used the knock down connectors (14mm) for a client project and would use them again in a heartbeat if that was a requirement for something I'm building.

I'll make no secret about the fact that I'm a very satisfied Festool owner. My only regret was waiting several more years than I should have before buying the Domino and I'm not saying that to show off. I really like and respect the tool...

[Steve Mathews]

Based on the comments so far it seems to me the best system to join long grain together would be one thin and continuous spline. It would provide alignment along the entire length but not take up too much surface area for the glue. It may however be more difficult and time consuming to accomplish if cost and production is a consideration. That's my take on it so far.

[Jim Becker]

A spline is a perfectly valid way to do the deed. It can be easy, too...use a slot cutter with a bearing in a router and run it down the edge of both pieces, again, indexing on matching surfaces, such as the intended tops. That puts your spline at the same level from the top of the boards. Make a spline that is a snug fit for the slot you cut with a little room for glue behind it in the slot. Glue and clamp up. Done.

[Prashun Patel]

“Best” in this case is moot. All those methods will work fine and You will not be able to tell which was used.

A continuous spline is probably used not because it’s stronger but because it’s easy to cut the slot.

I am no pro, but I have made enough panels To know that a gappy joint is almost always caused by improper jointing and gluing - almost never because of the choice of reinforcement.

[Matthew Hills]

Would your spline show at the end of the joined panel?
(this sometimes happens with the other joinery systems as well, but usually after trimming to length and realizing you cut into one of the biscuits)

Gluing up a flat panel is also a good technique to develop. (or get a big J/P or get good with hand planes :-)

Matt

[Warren Lake]

neither, its just wasted time, on top a lamello will not give you consistent 100 percent flush every where joint.

[Mike Henderson]

If what you're concerned about is alignment of the boards in the panel, use cauls and skip any of the other things to align the boards.

Mike

[Doug Dawson]

A spline is a perfectly valid way to do the deed. It can be easy, too...use a slot cutter with a bearing in a router and run it down the edge of both pieces, again, indexing on matching surfaces, such as the intended tops. That puts your spline at the same level from the top of the boards. Make a spline that is a snug fit for the slot you cut with a little room for glue behind it in the slot. Glue and clamp up. Done.

The easiest way of doing this is a shallow-depth tongue-and-groove on the router table, provided you have pressure rollers attached to the fence etc. to hold the slot etc. even to the table (or else that defeats the whole purpose.)

Biscuits are a bit more expedient for the impatient. Provided they fit right.

[Jim Becker]

Would your spline show at the end of the joined panel?t

Not unless you make the mistake of running the slot full length rather than as a stopped groove. Of course, for some, that would be a perfectly valid design element.