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I'm actually considering 3 possible methods, and one of them involved making two shafts with two cams on each with a screw to adjust the rotation of the shafts to lift the table up or down.. Rollers would be mounted to the underside of the table for the cams to push against...

The idea for leveling on that system would be to mount each end of the four shafts through threaded heim rod ends which could be adjusted up/down using nuts on their threads through a mounting plate..





The other method is to use four ACME screws and a bicycle chain underneath.. A smaller dive sprocket would be used for gear reduction, and on the opposite side a spring tensioned idler gear... and yes, set screw mounting of the gears on the screws for leveling of the system..

The reason I'm starting to lean this way is because with the cam method I'd have to install four 1/2" guide bars to lock x/y lateral movement of the table anyways.. and that means drilling the holes and installing shafts right where the screws would go anyways..

The other method I was considering was using a scissor lift type of mechanism, but I'm having a hard time figuring out how I would do 'leveling' of the table with that system...

Since I do not have access (anymore) to a machine shop for precision built parts, I have become a fan of designing everything to be adjustable! The scissor lift mechanism you mentioned could work. The "Leveling" adjustment I would use for each of the four corners would simply be an eccentric mounting method of the actual table-to-scissor lift mechanism. This could be accomplished with a common drill press. Simply stack 4 round pieces of plate steel, and clamp them together. Drill a center hole through them, then an offset hole (to serve as the actual eccentric). Disc brakes work so well on an automobile because of the clamping action against the brake rotors that they use. So, the locking method to employ here, would be to design the discs to be locked with either a second piece of plate, or a large flat washer using a bolt which would be threaded into the actual frame of the table. A lever could be attached to the outer perimeter edge of the discs (either tapped into the edge, or welded onto it) to allow for ease of adjustments in leveling each of the four corners. Or (since this SHOULD be a one-time only operation) a simple series of holes could be drilled into the perimeter of the discs, into which a small allen wrench, or punch could be inserted and used as the handle to adjust the position of the "eccentric" for leveling. I really miss having access to the machine shop where I used to work. But since the plant closed, I have learned MANY ways of achieving precision designs by simply designing the machines I build with similar adjustment mechanisms. There IS more than ONE way to skin a cat!