Thread: Parallel clamps are moving as they tighten causing my glue ups to “slide”

Originally Posted by Pete57

Interesting explanation on parallel clamps becoming parallel under pressure
https://www.youtube.com/watch?v=FwXVJusqv0s&feature=youtu.be

Good video. The fact that he reckons the jaws become parallel because of the bar deflecting is interesting. I think I was probably over tightening the clamps.

Most of the time I'll over cut my stock and flatten/shape/cut it back to exact measurements after glue up & clamping. On pieces that need to be totally parallel I use various clamping strategies, like this one:

https://www.youtube.com/watch?v=Il5vFKGv3Uc

I found getting even clamping pressure over the whole stock using clamps is pretty much impossible, especially when using different types of clamps. My Bessy clamps are probably my best Parallel clamps but even these are not perfect. Also the glue is squeezed out at varying degrees depending on the clamping pressure and this causes the timber or whatever you are clamping to be out of square or have a different width in places.

Two things that I have invested in that have helped me a lot when clamping, a thin air press vacuum bag and my
new assembly table, which I made myself.