MDF and Biscuits

[Alan Tolchinsky]

Hi All, What's the best way to biscuit join a hardwood border to 3/4" MDF? This will be for a table top with a piece of veneered MDF bordered by 3/4" walnut. Table size is 12x45" . I'm wondering what type glue will be best to hold well in the MDF and not "telegraph" in the MDF? Thanks Alan in Md.

[Howard Rosenberg]

the biscuit slots are reasonably centred, they won't telegraph, refardless of the glue. I use Titebond and Titebond II and have never had a prob. Howard

[Todd Burch]

Howard' method will work fine. I find that splines work best for me on long runs. 1/4" router slot cutter and a piece of 7/8" wide 1/4" ply for the spline.

[Alan Tolchinsky]

Howard' method will work fine. I find that splines work best for me on long runs. 1/4" router slot cutter and a piece of 7/8" wide 1/4" ply for the spline.

Thanks for the quick response! Wow! Todd, I can see where a single long spline might be easier to deal with than an bunch of biscuits. I'm going to try your way first and then maybe a biscuit glue up. Probably if the spline works and is easy I'll stick to that method if I know myself. :)
Biscuits seem to put a lot of time pressure on me as they seem to "lock" the joint quickly due to the swelling. I just don't need any more pressure during glue ups.
Thanks again. Alan in Md.

[Alan Tolchinsky]

Thanks for the quick response! Wow! Todd, I can see where a single long spline might be easier to deal with than an bunch of biscuits. I'm going to try your way first and then maybe a biscuit glue up. Probably if the spline works and is easy I'll stick to that method if I know myself. :)
Biscuits seem to put a lot of time pressure on me as they seem to "lock" the joint quickly due to the swelling. I just don't need any more pressure during glue ups.
Thanks again. Alan in Md.


What is your method of attaching the top to the apron? I usually use metal clips that rest in a groove in the apron and screw into the underside of the table top. Since MDF doesn't accept screws that well,what would you do? Thanks again. Alan

[Todd Burch]

I make my own clips. It doesn't take too long to make more than you need for any tabletop. Solid wood works best. This method is nothing unique to me; I read it in a book somewhere and adopted it.

The first picture is two views of the same clip. The single screw hole is countersunk and predrilled to allow the screw to slip all the way through. You don't want any threads catching the clip. You could vary from the sizes I show, but be sure the long grain extends out the lip that you create via a rabbet on the end grain. If you have short grain running the width of the lip, it will break right off.

The second shot shows a cross section of a top, apron and the clip. You can make the clip slot in the apron with a slot cutter or your biscuit joiner. Or, you could run a groove with your tablesaw all the way along the apron prior to assembly.

As the photo shows, make your slot low enough to cause the clip to pull the top down onto the apron. Be sure to size your clip screw so that you do NOT come through, out the top of the table. That would be bad. :eek: The clip could be coutersunk more than I show if your screws that are on hand are short.

Leaving the clip away from the apron a bit allows the top to expand or contract without the clip hitting the apron. The clip screw just needs to be snug. The clip will move with top and simply move in or out of the slot in the apron. No muss, no fuss.

Anyway, that's how I do it, others may have better methods.

Todd (Do those colors wake you up!!!)

[Alan Tolchinsky]

I make my own clips. It doesn't take too long to make more than you need for any tabletop. Solid wood works best. This method is nothing unique to me; I read it in a book somewhere and adopted it.

The first picture is two views of the same clip. The single screw hole is countersunk and predrilled to allow the screw to slip all the way through. You don't want any threads catching the clip. You could vary from the sizes I show, but be sure the long grain extends out the lip that you create via a rabbet on the end grain. If you have short grain running the width of the lip, it will break right off.

The second shot shows a cross section of a top, apron and the clip. You can make the clip slot in the apron with a slot cutter or your biscuit joiner. Or, you could run a groove with your tablesaw all the way along the apron prior to assembly.

As the photo shows, make your slot low enough to cause the clip to pull the top down onto the apron. Be sure to size your clip screw so that you do NOT come through, out the top of the table. That would be bad. :eek: The clip could be coutersunk more than I show if your screws that are on hand are short.

Leaving the clip away from the apron a bit allows the top to expand or contract without the clip hitting the apron. The clip screw just needs to be snug. The clip will move with top and simply move in or out of the slot in the apron. No muss, no fuss.

Anyway, that's how I do it, others may have better methods.

Todd (Do those colors wake you up!!!)


Todd,

Very cool pics. I like your method better than using metal clips. Wood is usually nicer to look at even though you don't see these. But would you feel comfortable screwing these into an MDF table top to hold it to the apron? It seems like screws would pull out of the MDF. Thanks for all the help. Alan in Md.

[Todd Burch]

Alan, yes I would screw into MDF using coarse thread drywall screws (unless the table is going to see rough use or be moved a lot). If you feel leary about screwing into MDF, you could always glue an additional plywood block or solid wood block to the bottom of the tabletop and then attach the clips to that instead of directly to the MDF.

As with "things" like this, if you have concerns, remember that you can always make up a sample joint and see what it takes to break it. I do this frequently.

[Alan Tolchinsky]

Alan, yes I would screw into MDF using coarse thread drywall screws (unless the table is going to see rough use or be moved a lot). If you feel leary about screwing into MDF, you could always glue an additional plywood block or solid wood block to the bottom of the tabletop and then attach the clips to that instead of directly to the MDF.

As with "things" like this, if you have concerns, remember that you can always make up a sample joint and see what it takes to break it. I do this frequently.

Thanks again Todd. I can't wait to do some veneer work and make some furniture. I got my press working great and am waiting for veneers to arrive. I'll post pics when finished to show what your help and my work has accomplished. Alan in Md.

[Jeff Skory]

Todd,

Great pictures (again!). You definitely make good use of your little CAD program. Very nice explanation for this tip as well.

[Chris Padilla]

McFeely's sell "confirmat" (or something like that) screws specifically for MDF securing. They really do work.

[Alan Tolchinsky]

McFeely's sell "confirmat" (or something like that) screws specifically for MDF securing. They really do work.
Thanks Chris, I'll order some and give it a try. Alan in Md.