Clamping cauls help you join boards by keeping them flat, and building clamping cauls couldn’t be easier.
Joining boards is the first step in a lot of woodworking projects, especially if you are just getting started and working from recovered wood. If beggars can’t be choosers, they had better be builders because it isn’t likely you’ll just “find” the right piece for that project you’ve been sketching up. Of course you need clamps push the joints together when you are doing your glue-up, but as you apply that sideways pressure the wood will bend and twist and generally look for other ways to alleviate that pressure than just pushing the joint together. All this bending and twisting and bowing and cupping means you also need to apply fairly even pressure across the top and bottom of the pieces you are glueing together if you want to keep the piece flat (Protip: You Do).
Previously, I’ve used scrap 2x4s or lengths of questionably straight recovered hardwood to make cauls which I then clamp at the edges. Of course this requires four extra pieces of wood with flat faces and a clamp-able surface – as well as the four extra clamps. Finally, clamping on the ends means that the cauls will often bow AWAY from the middle of the workpiece – which is bloody annoying! Most importantly, it is awkward as FUCK trying to keep the myriad clamps in multiple directions minded while managing the setting glue.
Make your life easier by building clamping cauls like these – you’ll be glad you did.
Supplies for building clamping cauls:
It starts with the wood – I selected 4 long boards of 1×3 pine. Hardwood would be much better, but for now I’m starting
cheap budget conscious. Check the boards to ensure they each have at least one Straight, Flat, Unmarred edge – the faces don’t matter, but the edges are crucial so choose wisely.
The other supplies are some scrap plywood for the spacers, scrap 2×4 for the feet (I used a couple of the recent Jenga blocks that didn’t pass muster), washers to distribute the clamping force, carriage bolts (I’ll walk you through using threaded rod as a cost-conscious alternative), nuts, and some glue and screws to hold it all together.
Step One: Cut the Boards, Feet, Rod and Spacers
I’m not going to tell you how to cut the boards and spacers – it’s hard to goo too far astray if you understand the plan. As I mentioned, I bought a length of Coarse Threaded 1/2″ rod instead of carriage bolts for this project. The rod was ~$12 and each 12″ carriage bolt was going to be more than that and barely long enough. With a grinder and cutting disc you can easily turn the rod into the bolts you need – just carefully cut it to rough length (seriously, use your eye protection here people, the sparks will fly) and mash a bolt on one end! If you’ve got a heavy duty metal vise, that can do the trick, but I used a 4lb flat-faced hammer and our anvil. Make sure you wear gloves – the reverberation and the threads can be a bit much.
You’ll also want to counterbore and drill a hole through the feet to make room for the bolt and nut so that the feet will sit flat. Counterbore with a forstner bit to make space for the nut, then drill through with a 1/2″ spade for the rod.
Ready for Assembly!
Now our pile of supplies looks like this, and we are ready to get on with building clamping cauls!
Assembly is pretty simple, and needn’t be precise: EXCEPT THAT THE TOPS AND BOTTOMS OF THE BEAM NEED TO BE FLAT. That’s the whole point of the caul – to keep things flat. Build your beams with a spacer on each end and in the middle – use glue and some mid-length screws to hold them together.
Bolts go in feet, Rod goes through Beams, Washers and nuts go on top! Voila – you’re ready to clamp like a two handed pro!