I'm not impressed with the vac clamp either. It works but I'm not sure its good for cnc situations, there are better vac clamps out there. But much of it has to do with two things; how well your gasket is and how strong your compressor is. I don't think an 8 gallon will keep up with the vacclamp. I would imagine that thing will be recharging itself constantly, 2hp or not harbor freight compressors arent that well made anyways. Ran mine on an industrial ingersol rand and a 150 gallon 8hp?(I think) compressor and it worked well. Could hold my body weight but still had too much give to it for me to want to use it on a cnc router. Great as an extra hand when manually routing stuff though.