Has anyone used dominoes to join mdf? I've tried biscuts in the past and had problems with the glue swelling the biscut and blowing out the edge of the mdf. I don't currently own a domino or I would do a test. Thanks.
[OP]
Member
Has anyone used dominoes to join mdf? I've tried biscuts in the past and had problems with the glue swelling the biscut and blowing out the edge of the mdf. I don't currently own a domino or I would do a test. Thanks.
Moderator
Dominos would fare the same, wouldn't they? Dominos are just thicker, deeper biscuits.
I can't think of a way that would prevent blow out at the joint if it were torqued. MDF just doesn't have the grain strength to resist that.
I can see using it for case sides or shelves in some applications. In these instances, even biscuits may serve fine.
Contributor
On MDF I use Dominos but don't glue them (just for alignment). I glue the edge of the MDF and use screws instead.
Ed
Member
i have done it a number of times with no issues - dominos do not change size when exposed to glue
Member
This would be my approach for 3/4" or thinner MDF in making an MDF box for example or aligning side by side panels (no screws in such a case unless pocket screws from below).Originally Posted by Ed Weiser
I wouldn't hesitate to do this in any MDF thicker than 3/4". In 3/4" or less my concern would not be the Domino swelling but the MDF above and below the plunge swelling from the glue. I defer to Erik though as I have not tried this in 3/4" stock.
Last edited by Sam Murdoch; 01-26-2015 at 5:03 PM.
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WQJudge
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The times I have used Dominoes on MDF was when needing to extend the length or width of pre-made moldings. It worked fine, no swelling.
But if you don't own a Domino then this particular use is not worthy in and of itself to buy a Domino. Dowels would work the same and not swell. Biscuits are made intentionally to swell.
Member
FWIW I used biscuits all the time in 3/4 MDF to attach hardwood and it never blew it out. How close to the edges are you getting.
Not tried a domino in MDF yet.
Glad its my shop I am responsible for - I only have to make me happy.
Member
Festool claims that the "Dense beechwood tenons wont expand and telegraph through the work surface", and this is probably true if the work is wood, but my experience with MDF had been less than acceptable. I have actually split a piece of MDF in half with dominos on more than one occasion. The dominos may not expand but the mating MDF surfaces sure do, and driving in the dominos creates enough stress to split MDF. So use minimal glue and take caution. Or better yet, skip the MDF. It may be made from wood, but its not wood and doesn't behave even vaguely like wood.
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Just finished a large built in bookcase made from mdf and soft maple. I hate mdf but it was a lower budget item and it does paint up pretty nice. Anyway, used 5mm dominos to join the casework, the face frame to the case and the edging on the front of the shelves. No issues whatsoever but I always go light on the glue in the mortise and tap the domino home slowly.
Contributor
If i had to choose between a domino or biscuit in mdf,I would use the biscuit.In my opinion,the domino removes too much material for mdf.MDF gets pretty weak when it's that thin,then driving in a tight domino doesn't help the situation either.Of course,the grade of mdf has alot to do with it also.
Member
Maybe the differences of opinion on weather dominos should be used in MDF is related to how much wood glue is used and how much moisture the MDF absorbs from the glue? Maybe a polyurethane glue would work better because the mdf would not be absorbing water from the glue? Maybe a Polyurethane glue would be worse because the glue itself expands which may cause problems? Maybe a 2 part epoxy might be the best glue due to mo moisture and no expansion of the glue?
Contributor
I was having the same thought. I wonder if people tend to moisten wood when using polyurethane when they don't need to. Too much moisture makes for too much foam and also weakens the joint.
Moderator
I've blown out plywood driving glue saturated dominos. I've learned my lesson. Keep the glue minimal or the pressure from driving the domino home can blow out edges. A few swipes of a plane can help provide room for the glue to escape. Or, cut wider domino slots if possible.
I've heard from some experienced ww'ers that no extra moisture is needed for poly glue despite what the bottle says.
Contributor
I suspect whether or not to add some moisture depends on where you're located and what you're bonding. I live in a relatively humid part of the country and wood moisture typically runs 8%+ except during heating season. Polyurethane adhesive will cure just fine when bonding wood at that moisture with nothing added and won't foam like crazy. On the other hand, I used polyurethane construction adhesive to bond a piece of corian to a strip of sheet metal. In that case I moistened one side before clamping. That cured without excessive foaming and seems to be holding well.
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