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MDF vs. Plywood for jigs, table tops etc.

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Forum topic by roer posted 1117 days ago 3871 views 0 times favorited 13 replies Add to Favorites Watch
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roer

48 posts in 1841 days


1117 days ago

Hi

All of us want the table top for our router table to be dead flat and our jigs and fences to be 100% straight. For that we need stable wood that remains as stable as possible under different humidity. The preferred material seems to by birch plywood, but why is MDF (or laminated MDF) so seldom the preferred choise ? As I know MDF is should be even more stable than birch plywood, or ???


13 replies so far

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1760 days


#1 posted 1117 days ago

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

View Bertha's profile

Bertha

12951 posts in 1295 days


#2 posted 1117 days ago

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

View Lee Barker's profile

Lee Barker

2163 posts in 1452 days


#3 posted 1117 days ago

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"

View woodklutz's profile

woodklutz

221 posts in 1370 days


#4 posted 1117 days ago

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.

View DrDirt's profile

DrDirt

2360 posts in 2344 days


#5 posted 1117 days ago

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.

-- "If we did all the things we are capable of doing, we would literally astonish ourselves." Edison

View jonasramus's profile

jonasramus

24 posts in 1577 days


#6 posted 1117 days ago

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

View Bertha's profile

Bertha

12951 posts in 1295 days


#7 posted 1117 days ago

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

View GregD's profile

GregD

606 posts in 1738 days


#8 posted 1117 days ago

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.

View Lee Barker's profile

Lee Barker

2163 posts in 1452 days


#9 posted 1116 days ago

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"

View Lee Barker's profile

Lee Barker

2163 posts in 1452 days


#10 posted 1116 days ago

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"

View Bertha's profile

Bertha

12951 posts in 1295 days


#11 posted 1116 days ago

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

View Lee Barker's profile

Lee Barker

2163 posts in 1452 days


#12 posted 1116 days ago

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"

View NBeener's profile

NBeener

4806 posts in 1775 days


#13 posted 1116 days ago

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

-- -- Neil

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