A Specification Every Drawing Should Have
- Thread starter Jim Wynne
- Start date
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Rebecca Bowes - 2010
Awesome!
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Teri - 2011
That will only work if you have the mating parts to check!!
For example: several years ago we were producing a part, no problems, all of a sudden, out of the blue, the frame wouldn't fit. But wait, we didn't change anything! After a trip to the customers (one of the big 3), we discovered they modified their mold (just a little) but it wouldn't mate with our part.
The statement I agree with, but becareful signing up to it!!!
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gleclair
This is a great point. Now if all parties involved with the manufacturing or servicing of the product could do this we would be living in a perfect world.
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Rebecca Bowes - 2010
I thought it was a great joke!!!
Not only that, the mating part has to be in specification. I have seen this many times over the years. In one instance we had mating parts and used them in qualification. The mating parts were QPL (qualified parts/product list at DESC). Turned out they were not to spec...
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David DeLong
This is a great point. Now if all parties involved with the manufacturing or servicing of the product could do this we would be living in a perfect world.
If the mating features were reflected in appropriate GD&T, then they would fit.
If you have positional tolerances at MMC, figure out the virtual condition size and then compare the virtual condition size of the mating part. The hole's virtual condition size should be a bit larger than the pin or else - won't fit.
The virtual condition size on a hole is its smallest allowable size and then subtract the positional tolerances shown in the FCF. The pin's virtual condition size is its largest allowable size plus the tolerance shown in the FCF.
I would never use a mating part to qualify its mating part since we really don't know if the mating part is inside the specification or not. Get an attribute fixture made for positional tolerances at MMC. This gage is the mating part made in the worst possible condition. If it fits the fixture, it will work.
Each new drawing should be reviewed in this manner but does it happen? I don't think so.
I would never suggest placing on a drawing that the mating parts should fit together. They should be drawn so that they do fit.
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Rebecca Bowes - 2010
Nice. I agree, the design stack up should ensure that the mating parts will fit together if they are in spec.
I agree wholeheartedly. I posted the the thing in the "Funny Stuff" forum because I think it's funny, but in reality it's a sort of CYA thing that wouldn't be necessary if things were properly designed.
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