Where to use my MDF?

[Stuart Welsh]

I'm in the stage of outfitting my new shop with equipment and with that comes the shop built items such as: Table Saw Out feed and Extension tables, Torsion box table, Wall and base cabinets, Shelf units, Rolling carts for stationary tools etc list can go on and on.

I have 5 full sheets of quality 3/4" MDF that was given to me. I'm trying to decide which items listed above are good uses for MDF either in entirety or partial. My thoughts are this: Some of my cabinetry or shelves will be painted so I know MDF is a good choice for a smooth finish. The torsion box and extension table seems like good uses although I have seen regrets posted at using 3/4" for a torsion frame as it is so much heavier than one built with 1/2". Shelving seems like a good use though I suspect I'd need to front all the edges with wood to deter sagging.

What are your thoughts?

Stuart

[Peter Aeschliman]

MDF certainly has its place, but having worked with it a ton over the years, I've learned that I don't like it for most things...

I don't recommend it for any surface that will get wear (outfeed table surfaces, counter tops, bench tops, etc) because it dents, scratches, chips, and sags (unless properly supported). Cover it with a sheet of melamine and cover the edges with hardwood if you plan to use it that way and you'll be good to go. I also don't recommend it for things that will be moved around (cabinets on wheels, flip top bases, etc) because it's really heavy. It also does really poorly anywhere there is water- another reason not to use it for a work surface since some finishes are water based. I also don't like it for base cabinet carcasses for that reason, depending on your situation. It could get exposed to water from dripping cars, or wicking moisture through a concrete slab, etc.

As you may know, you need to seal it with an oil based primer before painting. Water-based will cause lots of swelling and will require lots of sanding between coats. The faces of MDF take finish really well, but the edge/end "grain" does not at all. You'll want to seal that first. The best method i've found is rubbing some lightweight spackle on it first. I read it on this forum. I didn't think it would work, but it worked perfectly. Others use glue size (watered down wood glue).

Wear a mask or have really good dust collection too. The dust is truly awful and really bad for you due to the chemicals.

My favorite use for MDF is in the panels of painted cabinet doors, for shop jigs and sacrificial fences, and for work surfaces if it's covered with melamine.

My $.02. Hope that helps!

[Jerome Stanek]

build an outfeed table and cover with cheap laminate from the habitat store

[Von Bickley]

I can't help you with your question...... I don't use MDF.

[george newbury]

I like MDF simply because I was able to get a lot cheaply. My primary use is "sacrificial" work surfaces.

shelves-small.jpg

I have about 10 pallet rack units (works out to about 80 linear feet of 4 foot wide work surfaces) which for the first shelf I put down a sheet of 3/4" PT plywood and a 3/4" sheet of MDF on top. It's an excellent smooth surface and with moderate care lasts a while. I expect I'll have to replace them some time but I wanted a wood like surface quickly and didn't have time to join a ton of pine boards.

[Peter Aeschliman]

Oh, and be careful with screws. Always pre-drill with countersinks before using countersinking screws, and stay away from the edges. If you are screwing two pieces of mdf together, pre-drill your hole into both pieces, and make sure the entry side of the holes on both workpieces are countersunk. if you don't countersink both pieces, the MDF will lift on the second piece at the intersection and the workpieces will not butt up against each other snugly (you'll have a gap). In other words, the MDF lifts and creates a mound around the screw.

Between all of the nuances I've mentioned, and due to its weight and horrible dust, i think you can see why it isn't my favorite. Lots of WW magazines use the heck out of MDF in their shop projects. It's great that it's inexpensive, and it's the best material for a small handful of things... but i think the magazines over-recommend it. I now buy plywood mostly.

Don't throw it away, it has its place. You just need to know the limits of the material.

[Mike Heidrick]

As mentioned before - laminate on top makes it excellent and I like a hardwood edge like oak attached as well. I do that with biscuits. Double up two layers of mdf, hardwood edge 1x1.5, cover with laminate = excellent extension table and outfeed table.

[Tom Clark FL]

I have used some MDF for bench tops because it is cheap. However, at 91 lbs per sheet it is not light, or strong, and will not support itself. Plywood is used for strength in vertical surfaces. Photo one shows a 40x80 assembly table. It has two layers of mdf for a top. On top of that is a sacrificial sheet of replaceable Masonite as a wear surface. It is 10 years old and holding up well.

Second photo shows a shop cabinet built mainly for the storage of the drawers. The top gets little use other than to lay tools on it, so that top is two layers of mdf. One layer just sags too much. The stuff is far too weak to use as shelving. I soaked the top with polyurethane, as mdf will soak up anything spilled on it unless it is painted. It was still drying when this photo was taken.

[Rick Potter]

Like Mike says. A couple layers of MDF with Formica on top makes a great work table, outfeed table, etc.

[Mike Cutler]

Stuart

I would just put it against a wall until you know more what you want to do with it. I've used it for many things in the shop, but the most consistent use has been a sacrificial top for my work bench and protective cover for my table saws when not in use.
It's a little heavy for full sized router templates, but it would certainly work for template work.

3/4" MDF is too heavy for a torsion box of any size. The principle advantage of a torsion box is supposed to be light weight.
I saw Platt Monfort build an engineered box beam out of two 1x6's and poster board, about 8 feet long. He then placed it on two saw horses and stood in the middle, with the structure supporting his weight. It doesn't take much individual material strength/weight, if the total design concept is correct.