Clamping without Damage

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If you have some work fashioned from thin sheet metal, what do people do to preventthe work from being crushed or marred by the clamp?  Putting some sacrifical shimsbetween the work and clamp is one idea, but even so it may be hard to get a large clampinto some thin sheet work that's made from circular or rectangular tubes withoutclamping onto a whole tube (rather than one surface) risking crushing it.  Could a large bolt be tightened through a hole in the work and the clamp attached to that?We're probably talking < 80 amps.
Reply:clamp to a magnet with a post maybe?MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Hmm.  If it was a magnetized piece of iron I could see that working, but aren'tmost permanent magnets ceramic, and therefore not conductive?  Dependingon the resistance I'd probably melt it.  Given only a single response, I guessclamping issues are not too big among the folks here.
Reply:If the item is small and fragile some people set the item up in sand.  If you really need to clamp look for light clamps or items used in sheet metal assemblies such as for heating and ventilation.
Reply:Lightly clamp with a pair of vise grips, then put the ground clamp on the vise grips!Worked for me in the past.Flash
Reply:You don't have to clap it that tight, just enough to hold it until you can tack it. After all it's sheet metal.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Depending on the project, though at 80 amps I doubt what you're welding is so thin as to have a work clamp damage it, you might be best off with a grounded work surface. Take a piece of sheet and set your work down on it and clamp onto that.
Reply:Originally Posted by ericmHmm.  If it was a magnetized piece of iron I could see that working, but aren'tmost permanent magnets ceramic, and therefore not conductive?  Dependingon the resistance I'd probably melt it.  Given only a single response, I guessclamping issues are not too big among the folks here.
Reply:You trying to clamp the parts together, or clamp the 'ground' to the parts, or both?Plain old spring-clamp type of ground clamp should be able to grab onto the edge of the sheet metal just fine.  The spring tension shouldn't be all that much to damage some sheet metal, unless your clamp was made by/for Hercules or doubles as a grip exerciser  or unless the sheet metal is really-really thin.Or you just use the already mentioned magnetic ground clamp attachment.  The magnet sticks to the sheet metal and holds the brass post tight against the work and you clamp your existing ground clamp or cable to the attachment.Neat trick about using a pile of sand to help hold parts in place as you tack them together.Clamping is often an issue.  You may not have enough clamps, the right size/type of clamps, awkward clamping angles, no way or where to clamp onto, etc.  So you have to get creative.  The best laid schemes ... Gang oft agley ...
Reply:I have a large block 2x4x4 of aluminum with a hole in it, I clamp my ground to the block and lay the block on the sheetmetal.  Or I use thinner pieces (3/8") of aluminum and sandwich the sheet.Have we all gone mad?