How much can a vacuum chuck hold vs an electromagnet?

admin

I know the question is dependent on voltage, size, current, vacuum and windings but here's what I'm curious about.I have an older milwaukee 4200 mag drill that I like, but has a blown up electromagnet.  My first thought was to re-wind the electromagnet but lately, Ive been doing more stuff with wood and plastic and was wondering instead, if I got a vacuum chuck like this one:http://cgi.ebay.com/Vacuum-Chuck-VTZ...item41508ebba2and made an adapter plate to mate it with the bottom of my mag drill base, I'd have a pretty sweet rig I could use to drill straight holes into just about anything flat enough for the chuck to sit on.What I'm curious about, is if it will be enough to hold onto steel being drilled with a small vacuum pump?  Their ebay auction shows them milling aluminum so I can't imagine its terribly weak, but don't know where to find the specs on the milwaukee electromagnet so I can compare.  Thoughts?  Ideas?
Reply:Should work fine as long as you have a big flat surface to clamp on.
Reply:A vacuum chuck has a max theoretical hold of ~14.7 psi (or the adjusted local absolute atmospheric pressure) times the surface area of the chuck.Allowing for a non-perfect vacuum and for quicker calcs, call it ~14 psi x Area.Circular area = .7854 x D^2  (the .7854 is from pi/4 to enable use of diameter instead of radius, if you want to use the radius then it's just pi x R^2 )So for a 3 inch diameter chuck, you could have a max holding power of about 99 lbs.  And that's with GOOD suction.  Crank that 3 inch diameter chuck down to max micron level vacuum (HVAC or lab level vacuum pump there) and you could MAX out at about a whopping 104 lbs.A 3 inch electromagnetic chuck usually has waaay more hold than that.  A Milwaukee 4270-20 1/2 inch chuck mag drill lists a mag force of 2300 lbs on 1 inch steel plate and a downforce (drill point force) of 750 lbs.  So the vac system wouldn't let you crank down on the drill handle (quill handle) much before popping right off of the work surface.  And never mind even trying to figure out the torque reaction from the drill bit on the work surface twisting the vac base right off of things.A vacuum chuck can be handy, but mechanical or electromagnetic chucks can generate waaaay more holding or clamping force.  Sometimes a vac is enough or the only real solution (vac bagging for instance), but for total power the others usually 'win'.  The best laid schemes ... Gang oft agley ...