slaving axis's

hello all in CNC land, wondering how i might be able to slave axis together
on a machine. specifically on a gantry style with motors on both sides.
Can the ±10v (for servo) be spliced together before the servo amps, and the
step-direction wires be spliced, or is the amperage not enough?? how do
they do it in the industry? encoder off the first axis driving the
second?--Dave L.