For more information on sash clamps, see our beginner site Common Woodworking.
These steel clamps from Screwfix UK are not too heavy though they are heavier than the alluminium box clamp I use daily. They are tidy and neatly made and it’s handy to have steel clamps because of the extra torque you sometimes need, especially on heavier work such as joinery. These clamps are relatively kind on furniture pieces and general joinery too and especially so if you remove the hard corners of the bar.
I improved the clamp in a couple of ways to bring them on a par with say the old Record clamps I am accustomed to of the past. I have never liked the ‘pistol-squeeze-grip’ clamps and neither the Bessey clamps because of weight, jaw size and type and cost. They don’t suit me or my work.
First things first, these clamps are really called cramps and from now on I will revert to their original name as this seems to me more appropriate. The cramp seems to me well made from quality materials. The bar is sufficiently stocky without being unnecessarily over weight or oversized. The screw thread seemed well made and freely moving in the clamp head. I felt that the corners of the square-edged threads were to sharp.
To remove them, I used a large triangular saw file placed in the recess of the thread so that two faces caught the two sides of the threads. I then turned the thread with the bar and allowed the file to travel along the thread to remove the corners.
I then rounded the corner with 150-grit abrasive and again waxed the whole. The clamp heads were nicely finished on the faces with a gentle camber which I liked and all of the corners were rounded and easy to the touch. Cramps are of course used with additional blocks of flat wood to cushion the work and so no further refinement is technically needed, but I like protective material, plywood or softwood actually attached to the faces of the cramp heads themselves. This saves fiddling during cramping. Because the faces are slightly cambered, wood didn’t sit flat on the heads.
I took a length of pine and used a large hollow moulding plane to create a slight inner hollow to the wood and cut them to length. You could do this with a gouge too, or you could shape a block to a rounded face and use coarse abrasive paper to round the face of the wood pads. This only takes a few minutes.
After that I removed all traces of factory oil from the cramp. The cramp works perfectly and is set up up for fine furniture making and joinery.