MDF vs. Plywood for jigs, table tops etc.

Actually, MDF is probably preferred by more people for such things than plywood just because of cost. High quality birch plywood is great if you can afford it, but MDF works very well too. Unless your workshop is underwater, the MDF should be plenty stable.

I think some people avoid MDF because of the nasty dust it generates when you cut it…not because of stability issues.

-- jay, www.allaboutastro.com

I use MDF sandwiches because the edges are friable. Nothing wrong with MDF in my book!

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

And the dust issue is blown way out of proportion. Yes, the dust is bad, but simple precautions are all that’s required. It’s a great product, widely available, reasonably priced, easy to work, and usually delightfully flat. Put on the mask and cut, that’s my thinking.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

The problem I find is attaching it. What method do you guys use to joint. I use dry wall screws and they tear out.

-- honing my craft one mistake at a time.

I like the stability of the MDF – perhaps weight factors in as well – but jigs and templates stay nice and flat. I have a tablesaw sled made from birch ply and it warped a bit – - just enough that there is a “bump” or ridge between the left and right sides of the kerf.
Next one will be MDF – but it always seems that more attention is spent to make the NEW stuff than going back and remaking the old.

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

Both plywood and MDF have there pro’s and con’s. Generally the best idea is to pick the one appropriate for the application.

MDF Pro’s: very stable, very flat, less expensive than high quality plywood
MDF Con’s: it is not as strong as plywood of the same thickness, it does not hold screws well, it swells terribly if it gets wet, the edges get easily damaged, it’s damn heavy.

Plywood Pro’s: is usually stable but can cup or warp, it can be purchased in a wide variety of veneers to match you project, it hold screws very well
Plywood Con’s: it’s very expensive if you buy the good stuff, it needs it’s edges covered if the pc is for show

-- Jeff, Deltona Florida

Clutz, I usually glue and pneumatically pin it for jigs. If I need screws, I usually use fine Kregs. I have a tendency to use Kreg screws for a lot of non-pocket applications.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

I have problems keeping the moisture off MDF jigs. It gets hot in my garage (Houston) and sweat becomes an issue. Things I care about get a coat or two of poly or I start with melamine and edge band any exposed edges.

IMHO MDF is more flexible than flat, so I usually plan for some structure to give it good support.

woodklutz – I use Kreg’s pocket hole screws mostly and drill a pilot hole at least part way. I also do the final tightening slowly by hand – they go from tight to blown out real fast. I don’t expect MDF to conform nicely to a flathead screw, so I would drill a countersink and use a conventional flathead wood screw before trying drywall screws.

-- Greg D.

MDF glues easily. I would not recommend screws into the edge. Perhaps a staple as a clamp. Biscuits work splendidly. Or you can cut a kerf and make 1/8” spline stock out of plywood.

As soon as you try a mechanical fastener in the edge, you’re running a strong risk of changing that dimension.

Performax screws are the right ones if you insist, but then you gotta buy the $25 bit.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

Confirmat, not Performax!

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

Lee’s got drumsanders on the brain;)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

It’s the constant drumming, not the sanding, that makes me weird, Al.

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

With MDF, I’ve had great luck using Spax screws.

-- -- Neil

Does anyone make a confirmat or spax screw in a 1 1/4” length, #8, 7, 6

-- It isn't as easy as the demos make it seem.

I have used Extera (exterior grade) MDF with great success. More expensive than the regular stuff, but is almost bullet proof. I even used it on porch columns of a home. Won’t work UNDER water, but it sure does not vary with humidity.
Check it out.
Bill

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