I just had a need to clamp some parts together in a tight space and none of my other clamps would work. I came up with the spring loaded clamp and thought that if any of you need one I can email (PM me) you the OBJ (for 3D Printer) file. Similar clamps use a little wedge but often slip. The pressure is applied to the moving jaw and is adjustable for varying work thickness. The hole in the adjustable ferrule is .05inch (1.27mm) and can be drilled out and tapped for a screw. The screw only needs to be finger tight to avoid slipping. The spring is about .31inch (7.8mm) ID and the length can be about 1inch (25mm)
After I printed these I saw the need for making this a one hand operation, so I added the "L" shape trigger to pull the sliding jaw back. It will be cemented to the sliding jaw as seen in the assembly CAD drawing. (I will upgrade mine tomorrow.)
Lew

Ronald, adding a gripping surface can be done if needed. These clamps are small and the spring's (that I used) pressure is not that great. An alternative would be to make some pads using thin rubber and cement them in place.
Lew

I posted this clamp on line for anyone to download for free. This also includes instructions. Lew

https://www.thingiverse.com/thing:7360636