August 20th, 2015


(no subject)

It must be not possible to insert the component into a jig upside-down or the wrong way round. This is not usually difficult to ensure, but it is surprising how often it is forgotten, even by experienced designers. With no intended aspersion on anyone in the machine-shop who may use the jig, it is always assumed as a matter of course that if a component can be loaded into a jig the wrong way round, the operator will do it considerably more often than otherwise. After all, he is not paid to think, and it is not fair to expect him. In any case, he just may not know which way he is supposed to load the part, particularly if the jig is adaptable to a variety of components, or a left-hand and right-hand component of the same form.
The writer knew of a case, some years ago, in which one component out of a whole batch was found to have been drilled wrongly. The inspector, the shop foreman, the draughtsman who designed the jig and the toolmaker who had made it, all tried for an hour and a half to get the component into the jig the way it had been drilled, without success. Finally, in desperation, they took it to the operator who had drilled it, and he couldn't do it either.