TABLE OF CONTENTS In most engineering applications, situations arise where components are required to fit interchangeably with a variety of other parts. For example, one factory may be producing shafts that are required to be a slide fit in bushes being made by a totally different factory somewhere else, even in a different country. Each of the parts made say, by factory A must achieve the required fit in all of the parts made by factory B and vice versa.
The same requirements exist in the manufacture of mould tools and mould tool components. For example, standard parts suppliers like DMS, DME, Hasco, etc. market a number of components such as guide pillars, ejector pins, return pins, sprue bushes and so on. Each of these must be manufactured to sizes that ensure they will fit satisfactorily into other mating components or holes that have been machined into the mould tool by the toolmaker. Equally, the toolmaker has to ensure he makes the mould tool so that when buying these parts, they will have the required fit in the tool.
In order to do this successfully, both parties have to a work within a tolerance. A tolerance is the difference between the smallest size and the largest size the component may be made to. The tolerance zone must satisfy two conditions:
It must be large enough for the part to be able to be made.
It must guarantee that the desired fit is achieved with its intended mating...
