I picked up about 9 identical 600mm x 350mm offcuts of 18mm MDF on one of my trips to Wenban-Smith a few weeks ago.
One reason I got them is that (by eye) they looked about the same size as the tops of my folding workbenches
and I had a few ideas about using them to mount power tools and machinery to them, as per this instructable.
Having got them home and offered them up, they’re not a perfect fit but they’re good enough. (If they hadn’t turned out to fit so closely then I had some other ideas for what to do with them).
If I get a benchtop bandsaw or pillar drill or morticer then I’ll probably build a base for them too.
In the mean time I thought I’d build a plain table that I can rest my planer thicknesser on.
This is effectively a dry run, allowing me to think about the method of fixing the two layers together and how to mount the resultant laminated table top on my folding workbenches.
I had considered drilling some 18mm holes in one layer of the MDF, lined up with the dog holes in the work bench, then glueing the two layers together and inserting 18mm dowels into the resultant pockets, but this seems excessively complex and the dowels are likely to be damaged if I remove the table top and rest it on the rough concrete floor of the garage.
I’d also considered a batten at each long edge, which would allow me to clamp the top onto the bench by opening the jaws until they met the batten and would hopefully be nice and stable when removed from the bench and resting on the ground, but the workbenches are built in such a way that I wouldn’t be able to wind the handles if anything protrudes beyond the front of the front jaw, so that idea was out.
I’ve therefore gone with the obvious option – a length of timber attached to the center of the MDF which can be clamped in the jaws of the workbench.
The timber is just an offcut of 4″x1″ planed pine I had lying about. It’s perhaps a little short (the MDF is about 14cm longer than it) but it should do the trick.
I had to run it through the planer a couple of times on each edge to get it down to a size that would fit between the jaws of my Perform workbench at their widest opening. (As my Draper workbench jaws open marginally further it should be fine on there too).
To get the position of the wood right I clamped the MDF to the workbench and drew along the inner face of each jaw with a pencil. I also marked the front edge and top face to make them easy to locate, then flipped the MDF over and clamped the wood offcut an equal distance from each end.
I didn’t want to screw into the MDF as it wouldn’t give a particularly great fixing, so I drilled some countersunk holes through the top face of the MDF into the wood. The heads of the screws will be hidden by the second layer of MDF which will be glued on top.
To ensure the holes weren’t skewed I used my Axminster drill guide with my trusty Axminster White AW1050HD hammer drill (obviously not in hammer mode!)
I drilled the pilot hole first, then used it to locate and drill the clearance hole and countersink simultaneously with a combined drill and countersink.
I then covered the back of the timber with a coating of PVA, spread out with one of my disposable glue brushes and screwed and clamped the MDF to it, then wiped off the excess glue with a damp cloth.
After a decent interval to give the glue a chance to go off, I removed the clamps and flipped it over.
I ensured the area around the countersinks was smooth by paring off the high bits with a chisel and then drizzled glue all over the top face of the bottom layer of MDF.
Having spread the PVA out with the disposable brush I dropped the upper layer of MDF on and clamped the two layers together using some scrap bits of timber as cauls.
I then piled a selection of heavy tools on the middle of these cauls (as my clamps were only able to function around the edges of the table top):
A quick wipe with a damp cloth has removed the worst of the excess glue.
I noticed while I was aligning the upper and lower layers dry that they don’t quite fit together perfectly so once the glue is dry tomorrow I’ll use a flush cut router bit to improve the edges and this will deal with any remaining glue at the same time.