3/4" MDF & birch Plywood: What order for a laminated Benchtop?

[Mike Kelsey]

Deciding to build my first workbench w/ MDF, I originally thought of two layers of MDF with a layer of the birch in between (for bench dog stability). Is this good thinking or should the birch be the top layer? Also the birch is not quite as flat as the MDF, so I thought the MDF would flatten it out. Would it be better to add an extra layer of MDF and/or birch?

I plan to edge the bench with 3" of laminated 2x6 fir for perimeter dogs.

Thanks in advance for any opinions/advice

[Andy Muckle]

Mike,

My "my first bench" bench is two sheets of 3/4" birch plywood carefully laminated, with a 1/4" sheet of MDF pinned to the top. Some day I'll make a bench I can be a little more proud of, but this is flat enough for my purposes, fairly stout/stiff (at only 24" x 48"), holds dogs, and when the MDF gets too messed up, I'll replace it, and use the old sheet as a template to match the dog holes.

I like the replaceable MDF top sheet.

Andy

[david brum]

I don't see the advantage of adding plywood unless you need to make the top lighter. As long as it's supported underneath so it can't sag, three layers of mdf should make a great bench top. Just be ready for how much it is going to weigh when you have to move/install it. It could easily be hundreds of pounds. If you're adding a bench vise or two, you might want to think about how they will be attached, i.e. will they be screwed in? Screw holding isn't mdf's best point. Dog holes in mdf should work fine. By the time they ever wear out, you'll probably be onto another bench anyway.

One caution with mdf is that it will swell irreversibly if it gets wet.

[Tony Bilello]

I personally would put the plywood on top. It would be somewhat more durable and waterresistant than the MDF. Things just have a way of spilling.
If you are going to make bench dogs, glue and screw 2X4's lengthways under the bench top. Drill your bench dog holes through the ply, the 2 layers of MDF and the 2X4. The 2X4's will help stabilize the dogs.
I quit using benchdogs ages ago. I use a pin nailer and scraps and nail the scraps around the perimeter of my work in place. Brad nails leave very small holes. I strip, repair,refinish and build furniture for a living. You can do this for many many years without having to replace the bench top.
My benchtop is a double layer of plywood.

[Stephen Cherry]

I would vote for mdf core, with birch plywood as a top and bottom skin. THe plywood would offer some streangth in tension.

Speaking of benches, I just bought some solid core industrial interior doors that are very flat, and look like they would make a good bench. Plus they were a big 5 dollars each.

CRAIGSLIST 'MATERIALS' section is your freind if you want a cheap, good bench.

[Mike Harrison]

MDF is flat, but thats about it.

Stephen mentioned the best solution for a "first" general use bench, industrial doors. They are tough and stay flat across their 3 foot width. Lengthwise, I made 8" wide aprons using 3/4" plywood. I mounted the front apron using some door hinges so I could lift it to get tall things stored underneath.

These two benches, 8 foot Fire doors, are 8 years old now, and are still flat and solid as a rock. The bench with the RAS/Miter saws, now has a delta 12" turret saw on it.

http://i670.photobucket.com/albums/vv62/mikeinkcmo/WW%20tools/RAS%20Miter%20bench/P10100012.jpg