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I'm making a simple woodworking table (nothing fancy but want it to be sturdy + flat) and I'm looking for the best way to affix a 1/4" thick sheet of masonite/hardboard to a 3/4" sheet of plywood.

My thinking is that the plywood will likely not bow + warp but when glued (and possibly screwed) to masonite board it will be fairly sturdy + flat for most amateur needs.

Wondering if there is a particular type of glue I should be using, a particular pattern or method of applying the glue between the two sheets, and whether or not I should screw them together as well (and if so: type of screw, methods for preventing the screws to protrude over the table surface, etc.). My main concern with the screws is that countersink holes will run dangerously close to drilling all the way through the 1/4" sheet of masonite, and might even have the undesired affect of weakening the board...

Thoughts?

hotmeatballsoup
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1 Answers1

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You can adhere the hardboard to the ply if you want, but it's not actually vital that you do so and often in benches that have a hardboard top surface it is left loose. It's not there as a structural element but as a sacrificial surface that can in due course be replaced... or flipped over, the other side used and then replaced in most cases ^_^

When the top skin is left unfixed it is commonly held in by a solid-wood edging all around the bench surface which both looks good and protects the relatively fragile edges of the MDF or plywood that form the basis of the benchtop.

If you do want to glue the hardboard down you could use PVA, but if so I think it best to just sort of tack it down with spaced out dots of glue, not a full spread over the entire surface although you can do the latter if you prefer. Perhaps better options for the adhesive in this case would be contact adhesive or a slow-setting epoxy since with these you won't have to worry that the glue is starting to dry out in places while you're manoeuvring the hardboard into position.

You didn't ask about this but if you will be doing much hand-tool work on your bench I would suggest adding another layer to the table, either doubling up the plywood or using a layer of MDF (even particleboard/chipboard or OSB are fine for this) to add mass and stiffness, increasing shock absorbency.

A single layer of 3/4" plywood is perfectly acceptable as a working surface, many successful benches have this as a top, but certain hand-tool operations benefit greatly from the most damping of vibration you can afford to build into the bench.

Graphus
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    Just to carry the feelings on the fragility of hard and medium density fibreboards, they absorb liquids, they swell up and fray. Neither HDF or MDF are ideal for work surfaces unless you're ready to switch them out regularly. I much prefer a thin ¼" ply topper. You can even sand out the worst bits that MDF would just explode at. – Oli May 09 '18 at 14:32
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    @Oli, I think that exaggerates the fragility of MDF slightly, even the standard stuff can make a very long-lasting workbench — as many long-lasting workbenches have demonstrated :-) And there is always the MR-MDF option if the builder uses water or watery liquids at the bench. – Graphus May 10 '18 at 11:51
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    Could you clarify what is the edging to maintain the two pieces together without gluing? How do you attach the solid wood edging? Don't you have to glue that? – Nobita Sep 26 '22 at 22:32
  • @Nobita, it's just strips of solid wood; if you do a Google search for plywood and/or MDF workbenches you'll find many examples that feature such edging and the wood chosen and its thickness varies. You can glue such edging on, but it seems common to attach it just with screws (which is what I've done in the past). There's no reason one couldn't simply nail it on, other than any innate reluctance to use nails, and it would be a lot simpler than screws for many users. But I don't recall ever seeing this done. If I owned a power nailer it's definitely something I'd try on my next build. – Graphus Sep 26 '22 at 23:14
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    Thanks so much, Graphus! – Nobita Sep 26 '22 at 23:28
  • Graphus, I haven't been able to find a diy tutorial that explains how to apply this edging to hold plywood+hardboard together without gluing. Are you supposed to put one screw to the hardboard and one on the plywood? Is the edge supposed to wrap both boards? I can ask in a separate question too, if you prefer. – Nobita Sep 27 '22 at 00:06
  • @Nobita, you attach the edging to the main body of the top, the MDF or plywood, so that it makes a lip above the surface (basically you form a shallow recess that the hardboard will drop into). If you're careful you can do this so the top edge of the wood edging ends up pretty much flush with the hardboard surface. But it's hard to get it really exact so I imagine it's common to do what I did and carefully plane down the wood until you're level with the surface of the hardboard (you can also flush it very accurately with a router). – Graphus Sep 27 '22 at 17:09