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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?

  • Just to be clear, are you using the hardboard as the top sheet? – WhatEvil May 9 '18 at 8:50
  • Yes @WhatEvil, plywood on the bottom, hardboard is the top surface! – hotmeatballsoup May 9 '18 at 11:22
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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.

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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 9 '18 at 14:32
  • @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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