Worm gears (except for some very special designs) must have backlash to operate. Something in the range of .006 at the pitch dia. Their other limitation is top speed (sliding speed between the worm and gear faces) which is why they are not used very often in servo drives. Since speed is not a problem if you can live with the backlash it should work for you. Cone drive makes zero backlash, spring loaded worm gearsets but these are very expensive. Be sure to use the synthetic gear lube made for worm gears to minimize wear (this lesson I learned the hard way).
Bob
You can always spot the pioneers -- They're the ones with the arrows in their backs.