I have an workbench with an MDF top would like to seal the work surface and edges. Is a non-water based polyurethane a good choice?
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As good as any. But it's a workbench, and sooner or later it'll look like it.
Why not tung oil. It drys hard and can be wiped on any scratches that develop. Most of the tung oils available (Formbys for instance) will harden in the bottle after opening and exposure to air,so fill the container with marbles, pebbles ,whatever to exclude as much air as possible.
Keith
Would there be any benefit to the polyurethane over the tung oil? I'm also in the process of making a router table top from MDF. I saw one at Pat Warner's Web site and he finished his with tung/poly. Just a simple MDF top...nothing fancy. What do you think?
Whatever you use, thin it so it penetrates better. I used polyester resin, just no glass matting. 2 coats and while I should have made it smoother, I haven't dinged it yet.
"I cut this piece four times and it's still too short."
I've never done any MDF finishing so I'm not sure what to use. I would like to end up with a somewhat protected smooth finish. I'm also making an MDF router table top and would like to have the same type of finish that will be smooth and low-friction so that I can move the wood being routed easily over it
The easiest solution is wax and buff. If you ding it, so what. Just flip it over.
I would use laminate for the router table surface. You would have a hard time getting a more durable and low friction surface with MDF. Smooth, yes. Durable with tung, polyurethane or other thin penetrating oil, no. You can laminate right over MDF, but it stays flatter if you laminate both sides. A lot of places that sell laminates have damaged goods that they'll sell a lot cheaper than normal. Ask for the heaviest grade of laminate they have.
"I cut this piece four times and it's still too short."
Yes. with tung oil you can but a bit on a paper towel and wipe it on. No muss no fuss.
I have an workbench with an MDF top"
In that application, it should be considered disposable. Where I work, and for my home shop, benches are made of maple, with replaceable masonite tops, except for the molding room, those tops [replacable] are Teflon over maple again. Makes it real easy to scrape the spilled resins off.
WSJ
I find that poly coatings stay sticky for some time. Might be annoying for a workbench. You could get fancy and apply a 2 part epoxy.
I made a reloading bench years ago, geez, at least 10 years old now. The top is about 6'x2' and doubled up MDF. I thinned a quart of poly and just poured it on, brushed it around, let it soak, repeated until the quart was gone. It dried in a couple of days and to this day that top is hard, durable, and barely marred. Rather surprising really, considering the beatings it gets sometimes.
"If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man." - Mark Twain
I built some temporary countertops for a kitchen project once. They were only supposed to be in place for three weeks but ended up staying for almost a year. I put about five coats of oil based poly on and they looked and performed great. The husband wanted to keep them he said he loved them. The wife however wanted and got her granite.
I couldnt believe how cool the MDF looked once it was polyed. It kind of takes on a stone look and its durable.
In fact the table my computer is on right now is polyed mdf (father son project). Its held up quite well to four kids.
David Marks used tung oil and wax for a torsion box he made from MDF. Basically the same concept you have. Here's the link to the full article, click on "finishing touches" for the tung oil and wax finish.
http://www.diynetwork.com/diy/shows_wwk/episode/0,2046,DIY_14350_26946,00.html
Thank You
That episode was on last week, but it was a layout/assembly table, not a workbench for cutting, pounding, chisling, and other hard use. For this, I think I would use a more durable finish e.g., the polyester resin I mentioned before. Yeah, it smells and is a little sticky at first, but after wiping it down with lacquer thinner or acetone, it's not sticky at all and really hard to mess up. Oil and strong solvents have had no effect on it.I saw a small workbench at Menard's (a midwest HD/Lowe's competitor) and it was MDF with rounded corners and impregnated by some kind of resin. Really smooth and hard.
"I cut this piece four times and it's still too short."