文档介绍：Common difference and surface roughness
The modern technology is more and more strict to ponents sizeprecision request. Moreover, at present ponents have spread ineach place different factory production, therefore must makes thestrict stipulation to ponents sizes and the production,guaranteed they have the interchangeability.
Causes it for ponents sign note size to change in a stipulationsector, guaranteed they have the interchangeable technology to becalled mon difference technology. Allows each size certainly tohave in the stipulation scope changes the momentum, is called mon difference. For example, ponents size may express for20±, mon difference (size changes momentum) is .
In does not affect ponents performance in the situation, mustgive the size as far as possible mon difference, by falls theproduction cost to is lowest. The production cost reduces along mon difference elevates.
Some three expressions mon difference way: Unidirectional,bidirectional and limit way. When uses the positive and mon difference, adds to mon difference is been called thebasic size the theory size e up. When only allows the size tohave (or changes in a big way to the basic size sole direction, orchanges slightly) when change, is the unilateral tolerance. May(change in the size when the basic size two directions big or changesslightly) all may change, mon difference is bidirectional.