I don't know of any rack & pinion system that doesn't cost an arm & a leg. However, I have seen counterweights used effectively on a drill-press. This was a large drill-press in a machine shop. There was a small pulley mounted on either side of the head and a pair of cables running from either side of the table bracket up and over the pulleys to a weight. They told me it was rigged that way for quicker adjustment.