Attaching MDF to Plywood

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Forum topic by Adamal posted 02-26-2013 09:09 PM 5820 views 0 times favorited 6 replies Add to Favorites Watch
View Adamal's profile


58 posts in 2027 days

02-26-2013 09:09 PM

I’m building an outfeed table for my Unisaw and wanted to put an MDF top on it. I built the table with a 3/4” plywood top and 7/8” short so that I can slap a sacrificial 3/4” MDF top on it and the leg levelers to true it up.

My question is, how would you attach the MDF to the plywood so that down the road it could be replaced? I was going to countersink a bunch of screws down through the MDF, but was wondering if there’s a better way. I’d like to have a clean, flat surface without all of the holes.


6 replies so far

View PurpLev's profile


8536 posts in 3675 days

#1 posted 02-26-2013 09:12 PM

you can countersink the plywood base from underneath and screw it into the MDF top. that way the top of the outfeed table will be 1 flat clean surface. just takes a bit of getting down there when you need to swap it out (which shouldn’t be all that often).

make sure you use short enough screws that won’t penetrate through the MDF.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View Adamal's profile


58 posts in 2027 days

#2 posted 02-26-2013 09:28 PM

Thanks PurpLev.

I thought about that, but I can help but think about all of the times I’ve heard about MDFs poor screw holding ability.

I’ve never really worked with MDF before (aside from making new TS inserts). I’m just trying to avoid future problems. I suppose I could do as you suggest and if anything doesn’t work out, I could just try over again…

View Kazooman's profile


1031 posts in 1979 days

#3 posted 02-26-2013 09:37 PM

The screws should hold in the MDF just fine. There will not be any forces working to pull the screws out. The only forces (small at that) would be from work sliding across the MDF and they would be perpendicular to the shaft of the screws.

Do you ever use jigs or a sliding table with runners in the grooves on the saw? If so you will probably want to cut matching grooves in the MDF. On the outfeed table I built for my TS I made the grooves a bit oversized so there is no chance of binding. They are not intended to act as a guide for the jig, just clearance for the runners.

View Jackietreehorn's profile


150 posts in 1965 days

#4 posted 02-26-2013 09:38 PM

Could use knife inserts from the bottom… I’ve had good luck using those in mdf.


View crank49's profile


4032 posts in 2997 days

#5 posted 02-26-2013 10:38 PM

My workbench top is 4 layers of 3/4” plywood and topped with 3/16” Hardboard. The hard slick cousin of MDF.
The hard maple banding around the bench is the same height as the hardboard surface.
The hardboard is attached with double sided carpet tape.
Been holding perfectly for 2 years and I think it’s the perfect surface to work on.
I made a 3/4” hole through the plywood under the top on one end of the bench so I can push the hardboard up with a big dowel rod when I want to replace it.

View Adamal's profile


58 posts in 2027 days

#6 posted 02-27-2013 12:33 AM

Thanks for all of the suggestions.

Yeah, I plan on cutting a couple of channels with my straight bit so I can use my sleds and such.

I’ll probably just try the screws up from the bottom. As Kazooman said, there won’t be too many forces working against the MDF. If that fails, I’ve got a fresh roll of carpet tape from making my inserts.

If all of that fails, I’ll let my kids eat breakfast on it. It’ll get so sticky nothing will come off…

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