I'm trying to compare some different types of clamps.
I have some of these: http://www.screwfix.com/p/bessey-gh30-all-steel-lever-clamp-300mm/3156K?kpid=3156K&gclid=EAIaIQobChMI_bfIiqyO1gIVqQrTCh3c-gBOEAQYAiABEgLCAfD_BwE&gclsrc=aw.ds&dclid=CIHP5YysjtYCFauGUQodCB8AIA
in my workshop and I'd like to know which are best to use when requiring the highest possible clamping pressure. The site linked above shows the lever-arm clamps as having 8500N of clamping force but I can't find a value for a screw-operated sash clamp as shown in the second link. My gut says the screw clamp will have a higher strength but is there a general value for this type of clamp or can I calculate it somehow?