I am trying to design one or more Go No-Go gauges for incoming parts inspection. so I've done a bit of research and learnt a few of things about +- tolerances and other things but all of them were about circular holes and shafts. Something that i couldn't find anywhere and I hope someone here could help me about is how to design a gauge for some oval slits (like the pic). I want my gauges to inspect length and width of each slit in addition to their pitches. how many gauges is needed? is it possible to check length and width with one gauge at the same time? what about the pitches? what are the standard tolerances for designing a gauge that is inspecting distance not diameter?
Well, it seems like calipers would be just as easy, but your gauge would have a minimum length and width that you want to fit, and then the maximum length and width for the no-go. However, if either the length or the width is over sized, but not both, the no-go isn't going to fit, so you'd have to look closely at each slit. If these slits vary in width, a pitch gauge may not be feasible, and calipers would actually be quicker and more accurate.
this is exactly what I need. I want to make sure neither length nor width is over-sized so if one of them would be, the part is rejected. So in this situation I think I can use one gauge for both length and width, right?
by the way, the widths don't vary and pitches are fixed.
each part has 20 slits and we have to inspect thousands parts, in addition to the fact that the tolerances are to narrow, so I don't think caliper is that quick and accurate.
If we had a vendor that tried to send us bad parts, the entire lot would go back to them, at their cost, to sort out the bad ones. If that makes their delivery late, then that's going to cost them as well. If you make a no-go gauge that is the maximum length and width, it won't fit unless the slit is too long and too wide, so you may need a no-go for each. You may be able to make a pitch gauge with 20 nominal "male" features to verify that it fits, but I can't picture a no-go for pitch.
Good points, thanks. Just one more question:
What about the thickness of male features? Is it relevant to slit size or they should be as small as possible to just fit?
I don't know what actually goes into these slits. I suppose the gauge should be at the maximum material condition to ensure that the mating part will always fit.