Choosing a top thickness
How the thickness and weight of a bench top change how it takes a mallet blow and holds clamps.
A thicker bench top takes a mallet blow with less movement and holds a clamp with a firmer bite than a thin one. This note explains how thickness and weight change those two things, so you can judge a top for a tall garage workshop.
Why thickness matters
A mallet blow is a short, sharp impulse. The top absorbs it in one of two ways: it flexes, or the whole bench moves. Flex is the bending of the top under load. A thin top flexes more and gives a hollow knock and a bounce you can feel through the handle. A thick top spreads the blow through more wood.
Thickness changes three things:
- Flex under a blow, which falls as thickness rises.
- Grip of a clamp, which needs enough depth of wood to bite without the edge bowing.
- Depth for holes, since a dog hole or a holdfast needs solid wood around it to stay sound.
Thickness and weight
Weight and thickness go together but are not the same. Weight is the mass of the top, which depends on thickness, width, length and material. A heavy top stays still under a blow. It also makes a rolling or folding bench harder to move, and it loads the frame more. A thick top of light, soft wood can still flex more than a thinner top of dense hardwood.
| Thickness | Under a mallet blow | Clamps and holes |
|---|---|---|
| Under 30 mm | Flexes and rings; the bench may shift | Edge clamps can bow the top; holes are shallow |
| 30 to 45 mm | Some flex; suited to light assembly | Clamps grip well; standard pegs fit |
| 45 to 60 mm | Little flex; the frame takes most of the shock | Firm grip for holdfasts and deeper holes |
| Over 60 mm | Very little movement; heavy to lift | Deep holes possible; hard to move on wheels |
Laminated and solid tops
A solid top is one piece of wood. A laminated top is several strips glued face to face. Lamination lets a builder reach a thickness that one board may not give, and a laminated top tends to show less movement across its width than a single wide board. Look at the glue lines at the ends of the top. Lines that are open or uneven suggest a top that will not stay flat.
Checking a top
- Lay a straightedge across the top in several directions and look for light under it.
- Press one corner down and watch the joint to the frame for movement.
- Tap the centre and then the edge. A dull, even sound suggests more mass than a hollow one.
- Check that the top sits level on the frame. See setting bench height.
For the material and flatness of a top, see bench top. A vise needs a top thick enough to take its fixings, so see bench vise. Holes for pegs and holdfasts are covered in bench dogs and planing stops.