By backlash I assume you mean the looseness that occurs in the screw when, for example, you loosen the vice after having clamped something. I have a record quick release (had it for years) and it has a good bit of looseness. I am not sure how much since I never really paid it much attention. I just assumed it was the sort of looseness that is found in the screw mechanisms of lots of woodworking tools, e.g., planes. (Think of how many turns it can take to engage the mechanism to move the blade in a plane or to raise or lower the blade in a router. In the case of the router, you can actually see the source of the looseness: the screw on the height adjustment mechanism works well in mine, but the slot in the blades that the mechanism engages is way too large. ) Some of this looseness will be the result of wear, but it is quite common in new tools too. I have periodically wondered if such looseness in new tools is intentional or the result of sloppy engineering and manufacture. I can imagine reasons to want a bit of looseness. In the case of the router, if the slot were snug it might be very hard to remove and change the blade on my veritas router plane. In the case of the vise, maybe if the tolerances were too small, the dirt and grime from a shop would jam the vise. Just speculating here.