Festool Domino

[patlaw]

The consensus seems to be that biscuits do not add any strength to a joint. Therefore, how do Festool Dominoes provide strength?

 

[Mike Davis]

The dominoes are real wood with the grain going perpendicular to the joint of the pieces being joined.

Therefor much stronger than pressed wood chips.

 

[CDPeters]

Dominoes are also much beefier than biscuits...

 

[KenOfCary]

A Domino is more like a mortise and tenon joint than a biscuit is. In fact, it is referred to as a floating tenon in a lot of places. I sold my biscuit joiner when I got the Domino.

 

[Jeff]

Compare the dimensions and orientation of each type. The domino is a floating tenon and quite a bit thicker than a biscuit, hence they're much stronger in use. Biscuits are primarily used for alignment of 2 face joined pieces, but they're not really necessary for gluing and clamping the two edges together.




http://smakawy.com/53408/biscuit-tool-woodworking-creative-picture.html

 

[Pop Golden]

Who came up with the idea that biscuits provide no strength to a joint. True it's not a tenon, but the very fact that it's there provides alignment & strength to the joint. The furniture industry have been using biscuits for years if all they do is alignment that could have been archived with a clamping system.

Pop:dontknow:

 

[Jeremy Scuteri]

Who came up with the idea that biscuits provide no strength to a joint. True it's not a tenon, but the very fact that it's there provides alignment & strength to the joint. The furniture industry have been using biscuits for years if all they do is alignment that could have been archived with a clamping system.

Pop:dontknow:

This seems to indicate they don't really add strength.
https://www.youtube.com/watch?time_continue=443&v=8WH7T4b9l2g

It may also depend on the type of joint, for example a long-grain to long-grain joint or a long-grain to end-grain joint.

This seems to indicate that they do add strength, with more biscuits offering more strength than fewer biscuits.
http://www.woodworking.org/WC/GArchive98/Abstract/abstract1.html

 

[patlaw]

I didn't go through all of the testing linked above, but I would love to see a test of a glued butt joint with and without a biscuit.

 

[junquecol]

Norm Abrams is responsible for the bulk of biscuit joiner sales. He had one, so everybody else had to have one. Norm, "World's greatest tool salesman!"

 

[patlaw]

Norm Abrams is responsible for the bulk of biscuit joiner sales. He had one, so everybody else had to have one. Norm, "World's greatest tool salesman!"

Not only did I buy one because of him, I bought exactly the same one he initially used: Elu 3380. It's still sort of like new since I've used it 20 times in 30 years. I do plan to use it more, though.

 

[Jeff]

I bought exactly the same one he initially used: Elu 3380.

It's a Black & Decker

FYI. Biscuits aren't too bad for the right project. I'm surprised at how well they did in this working man's test.

https://www.youtube.com/watch?time_continue=5&v=_5PRdS3GISQ

 

[patlaw]

It's a Black & Decker

It's been a while, but I believe Elu was purchased by Black and Decker. It's certainly better than B&D quality.

In any case, here's another series of tests for joints. It's a pretty good demonstration.

[video=youtube;6cAUz_eCmbw]https://www.youtube.com/watch?v=6cAUz_eCmbw[/video]

 

[stevenross]

cheap alternative

https://www.youtube.com/watch?v=epPHaxDCv48

 

[FredP]

Who came up with the idea that biscuits provide no strength to a joint. True it's not a tenon, but the very fact that it's there provides alignment & strength to the joint. The furniture industry have been using biscuits for years if all they do is alignment that could have been archived with a clamping system.

Pop:dontknow:

absolutely correct Pop. the argument that biscuits add no strength is used to justify the cost factor of the domino. Fussytool prolly started that myth. I've used both and prefer biscuits. faster, easier and a lot less fussy than domino's IMHO. cost isn't my reasoning either as I have a top of the line Lamello biscuit joiner. granted the domino's add more strength as they are beech hardwood. biscuits are pressed cross grain like plywood. if you do your joinery correctly neither are a necessity.

 

[Tarhead]

The strength of a long grain joint to long grain joint...think gluing 2 boards edge to edge to make a panel... is in the glue joint. Biscuits AND Dominoes don't add additional strength to that kind of joint. The primary strength in a short grain to long grain joint when you use a mortise and tenon joint is the tenon and the wood surrounding the mortise. Which is stronger? The Domino. Can a biscuit be strong enough? Depends on the stress on the joint.

 

[McRabbet]

I generally use biscuits only when I need to insure board-to-board alignment in a flat panel glue up when the board may have some slight bow; I use dominoes when joining joints like rails and stiles or legs to an apron (i.e., short grain to long grain). They are strong and provide accurate alignment (or desired reveal). Time saver versus traditional mortise and tenon joinery in these cases.

Clarification: To reduce the confusion, I should have used the more common term "cross grain" rather than "short grain". A Domino fits into mortises that pierce the cross grain in a rail and the long grain in a stile, but the glue joint is dominantly long grain to long grain making them strong. Hope this helps.

 

[Jeff]

I use dominoes when joining joints like rails and stiles or legs to an apron (i.e., short grain to long grain).

I'm confused by the terminology which I see called many things.

A sketch of long grain in a board and why is it called long grain? Running parallel to the length of the board?

A sketch of short grain and why is it called short grain? 90 degrees to the length of a board?

 

[Jeremy Scuteri]

I'm confused by the terminology which I see called many things.

A sketch of long grain in a board and why is it called long grain? Running parallel to the length of the board?

A sketch of short grain and why is it called short grain? 90 degrees to the length of a board?

I have not heard of "short grain" before. I believe Rob is using it as a synonym for "end grain".

Picture a 2x4 from Home Depot. The grain that runs the length of the boards is "long grain". There are 4 faces that are 8 feet long each that have face grain. The ends of the board are......... you guessed it....... end grain. Because they are..... at the ends of the board. There are two faces with end grain on a 2x4.

Trying to glue "end grain" to "long grain" is a notoriously weak joint. This is where pretty much anything extra will add strength because the joint is so lousy to begin with.

Long grain to long grain joints, like the ones in a table top, are very strong. Especially with modern adhesives which are believed to be stronger than the wood itself. Adding something to a rock solid joint like this isn't going to make it stronger. Kind of like changing a wooden door out with a steel door without reinforcing the door jamb and expecting it to be more resilient to being kicked in by a burglar.

 

[nn4jw]

Mortise and tenons, floating tenons, Dominos all seem like viable alternatives for the type of joints mortise and tenons were intended for. Biscuits I've used for edge glueups only and then only as an alignment aide, not for strength. A biscuit just isn't the same thing as a floating tenon.

None of the projects I do are "production" and something like a Domino is more money than I'm going to spend given that I already have multiple ways to cut mortise and tenons. And a fancy edge gluing clamping system isn't practical for me for the same reasons thus making biscuits a useful technique.

If I was doing production runs I'm sure I'd consider all the various (expensive) options.

 

[JimD]

Dominos are a type of mortise and tenon joint. Their primary limitation is the size of the dominos. If we want to make a mortise and tenon joint in a project, we make it a little smaller than the pieces to be joined. With dominos, you can't do that (without making your own custom piece and linking multiple slots). Using multiple dominos helps but doesn't eliminate this limitation.

All the biscuits I have used have been hardwood, not plywood or particle board. I've never seen anything other than hardwood used, I believe it is beech. They are slightly compressed and swell when they are placed into a joint and glue is added. The biscuits do not add as much strength because they are not as big. They are wide but that isn't the direction you need, the biggest, a #20, is about an inch wide. So you get something like a mortise and tenon but it only goes 1/2 and inch or less into each piece to be joined. And the domino is only about 1/8 wide. The smallest domino is 4mm thick or about 1/6 of an inch. Even the little domino will make mortises about 3/8 thick. Because of the thin aspect of the biscuits, I think of them more like splines than tenons.

Dominos are quick but limited due to their width, not their thickness. With the bigger domino, you can get plenty of length for most projects, the little one is limited to 25mm - about an inch. But other than the limited width selection available, they make mortise and tenon joints just as strong as any other mortise and tenon. They just make the joints faster.

So is a spline joint equivalent to a mortise and tenon? Obviously not at least for most purposes. Does a spline add strength? Of course it does - but if you use one in a leg to apron joint or other improper application you will be disappointed. But all joints have to be properly applied.