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I have some 1/8" plywood that I use to make small boxes, organizers etc.

Since it is rough, a fast and neat way to smooth it is with a smoothing plane. Only a few light passes, of course.

Using bench dogs doesn't really work because the plywood is so thin and the bench dogs are higher than the piece of wood and the toe of the plane would bump into them.

Any trick to clamp thin wood so the whole upper surface is available for planing?

Andrei Rînea
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    Wanted to compliment you for realising that you can plane plywood, many people never think to try it! And it's so much more efficient than sanding. – Graphus Feb 03 '19 at 10:44
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    Just one other thing on terminology if it's of interest, in English the front of a plane is generally referred to as the toe (the back being the heel). – Graphus Feb 03 '19 at 10:45

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In some respects end stops (as seen on most planing boards and as built into many good benches) are the ideal for planing thinner stock. You can use dogs as these stops of course, they just need to be a raised to be a hair lower than the surface of the board you're working on. And ideally made of wood or plastic, definitely not metal!

But there tends to be a limit to how thin the material can be and for planing stops to still work well and unfortunately that limit seems to be just around 1/8" (3mm) — the workpiece can flex as it's being worked and sometimes simply jumps over the stop which is all kinds of bad. In addition the force exerted on the edges can slightly damage them, and plywood's edges aren't noted for being resilient.

Instead of individual stops like dogs or short rising stops create you can use a wide stop built into the end of the bench or clamped vertically in an end vice, clamped in a face vice (example on Pop Woodworking1), or a continuous strip2. But regardless of the stop type a thin workpiece can still want to jump across it and significant damage to it can result, from the plane itself, from the workpiece hitting anything beyond (including a smooth wall) or from falling to the floor where corner damage is almost inevitable.

So, I think the ideal solution is not to try to have the whole surface available to work on at one time.

Instead clamp the piece firmly down to the benchtop using one or more clamps, a holdfast (or equivalent) and just work around it/them. This is the conclusion I came to from working the surface of a lot of recovered hardboard and soiled plywood which I needed to scrape clean. In addition to being sure the workpiece will never jump over a stop it keeps it flatter, which will certainly help when planing thin plywood which is prone to flexing.

There is one further possibility you might want to try and that's to place the plywood onto a sheet of the non-slip rubberised stuff sold for lining drawers3. This is now widely used to hold workpieces in place during sanding and routing operations. I'm doubtful it will work well for planing very thin material (because of the flexibility of the material and how you have to press down on a plane) but you might want to try it for yourself before you rule it out.

1 I believe this style is based on one published by Robert Wearing in his excellent book, The Resourceful Woodworker.

2 When planing thin material I've rigged up temporary stops that span the bench using a strip of the same thin material I was working on, clamped firmly at each end.

3 Note this same stuff (it appears to be exactly the same) is sold by some woodworking suppliers, but at hugely inflated prices.

Graphus
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If you are going to be doing a lot of this kind of thin surfacing work, you might want to invest in a vacuum clamp. When combined with a small vacuum pump, these clamps can hold onto the flat bottom face of the plywood with surprising strength, leaving the top side and edges completely unobstructed and accessible to your plane.

There is a concern (raised by Graphus) that these clamps, if used as shown in the link, wouldn't work for planing because much of the wood would hang over the raised edges of the clamp such that when downward planing pressure was applied to those overhangs, the wood would flex, breaking the vacuum and the clamp's hold on the wood. That is an absolutely valid shortcoming of using the clamps as shown.

I am planning to buy a pair of these clamps for my work table (as soon as I can afford the required vacuum pump) but will be embedding them in my work table between some of the dog holes. My plan is to lay the clamp into a closely fitted hole, such that its' rubber gasket is flush with the surface of work table. That way, any thin stock which I hold down with these clamps would be supported on all sides by the work table surface. That will handle the issue that Graphus raised. I will update this answer with pictures once I get it all working.

Henry Taylor
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  • Those are an interesting alternative for holding work down, although I think it's hilarious that for the sample piece being shown the T-track clamps that hold the vacuum plates in place could be used to hold the workpiece directly lolz Now re. the OP's requirement, how would these work for 1/8" stuff? – Graphus Feb 05 '19 at 07:46
  • I'm assuming that the 1/8" dimension is the thickness since he is making boxes. If that dimension is the height or width, those boxes aren't going to hold more than a nail clipping or a few grains of sand. So, imagining a 1 sq-ft sheet sitting flat on a table such that its' "front" is resting 1/8" above the tabletop and facing upwards, the clamp would attach to the "back"; the broad flat surface which is touching the table. The advantage of these kinds of clamps is that they secure the wood without obstructing its surface or edges. Like gluing it to the table but with an on/off switch. – Henry Taylor Feb 05 '19 at 13:39
  • I understand how a vacuum works thanks LOL What I was getting at is 1/8" ply is flexible. These clamps are blocks that sit above the working surface, the least force put on material this thin supported on blocks will cause it to bow where the blocks aren't. This means planing would be impossible, and that's specifically what the Q is about — holding thin wood for planing. It's not asking are there neat techniques for workholding in general. – Graphus Feb 05 '19 at 18:46
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    @Graphus, good points. I considered including something to cover that during my original writing of this answer, In retrospect, choosing not to do so, weakened the answer. I will fix that now. – Henry Taylor Feb 05 '19 at 18:50
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Alternative recommendation for smoothing without the need for planing stop: a cabinet scraper (card scraper)

The other answers look to the work holding issue very well, and can definitely be used with a smoother plane. However, if you are only looking to smoothen, then I recommend an alternative to the plane: a trusty cabinet scraper. Since it is easier to position the scraper, you could clamp the plywood on the face to your bench and avoid the horizontal clamping and dogs. Then move your clamp and scrape the previously clamped area. Et voila!

Wikipedia page: https://en.m.wikipedia.org/wiki/Card_scraper

PhDeadlift
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