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

and some of these: https://www.toolstation.com/shop/p21813?mkwid=skw2cS478_dc&pcrid=142002554548&pkw=&pmt=&product=21813&gclid=EAIaIQobChMIlKXqkq2O1gIVL5PtCh2r

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?

  • recordpower.co.uk/category/tbar-clamps show theirs as 1.5 ton, how tight you can do them up is another matter.
    – Colin
    Commented Sep 5, 2017 at 21:35
  • I think your gut is correct here based on the values achievable with C-clamps, which fundamentally tighten in the same way (likely the exact same threading in fact). I know that those standard sash clamps are sometimes said to exert "more than a thousand pounds of pressure each" which sure sounds like enough :-) But seriously, the fact that Paul Sellers uses the extruded-aluminium ones for nearly everything now by his own admission suggests either of the above would be more than good enough for most applications.
    – Graphus
    Commented Sep 6, 2017 at 7:06


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