Tricks of the Trade – Holding Curved Parts:
Ramon Valdez makes a useful workholding jig.
Ramon Valdez makes a useful workholding jig
Holding curved parts can sometimes be tricky, which is not really surprising given that most of our clamping devices are designed to hold flat or square components. The choice always seems to be to risk damaging the component with your clamp or risk not being able to work on it safely. So, here’s a super quick way to make a jig using offcuts and scrap material. The jig provides support for the workpiece while leaving you with both hands free to line things up and make them secure.
I start with a thick billet of a timber such as poplar (Liriodendron tulipifera), which is cheap and in a lot of workshops generally available in large sections as offcuts. Any timber will do, of course. Then simply trace a curve (inner or outer will work) onto the block of wood. Cut the curve on the bandsaw. Note, with thicker material it will help considerably if your machine is nicely set up and cuts square to the table. When you’re done you don’t need to remove the saw marks as a perfect fit is not necessary and they increase gription.
1. Select a suitable block to make the cauls
2. Trace the shape onto the block
3. Cut between the lines
Attach a single piece of 3 or 4mm thick ply (MDF or hardboard will work just as well) with staples and glue to the bottom of the curved pieces, I’ll refer to these as cauls from now on and you’ll see why. I used a scrap piece of Baltic birch as it allows for some flex. Remember to space your cauls according to the item you intend to hold. I also attached a couple of support cleats made of 6mm plywood to each of the cauls so the whole assembly can be cradled in the vice.
4. Fix the cauls to a flexible base board
5. Attach some support wings
As you tighten the vice the jig flexes thanks to the thin ply beneath the cauls and holds your workpiece firmly. A useful tip when you are making shaped pieces is to save the offcuts as they will often provide the perfect caul for a clamping jig like this.
6. Drop the jig into the vice and you’re ready to clamp
