Quote Originally Posted by Jonathan View Post
I would definitely use a screw on both sides linked by a timing belt. You could use two motors but then it's more difficult to keep it square. A small amount of skew will stop you getting 0.1mm tolerance. Why do you want that tolerance for kitchen worktop? How are you going to measure upto 800mm long to the nearest 0.1mm?
It's not for worktop, it's for cabinet components. As for the accuracy issue, let me explain it thus- if I make a cabinet with sides 720mm high by 565mm deep, and a base which is 564mm wide and 510mm deep (the difference in depth is for the back panel which is rebabated into the sides at 510mm from the front edge, but which is fixed to the back edge of the base panel) and the sides are actually 565.5mm deep and the base 509.5mm then there will be a 1mm discrepancy where the side meets the base at the front. That much discrepancy would be clearly visible, and even more obvious to the touch. Also the cabinet will be slightly out of square if the top of the side is 565mm and the bottom of the side is 565.5mm

At the moment when such discepancies occur I have to sand the proud part down until it is level with the other part (my cabinets are made from birch ply rather than laminate, so this is feasible) but I would much prefer not to have to do that and am prepared to go to some trouble and expense (I'm expecting this to cost me a good few hundred at least) to end up with an accurate machine.