Hello, have been reading this forum for a while now, great source of information. Recently question came up about measuring method so I would like to get advise from the experts. Based on the drawing datum A is the surface of the the stamped part, datum B is is a hole without any positional tolerance and than there is a round slot. Length and width of the slot are dimensioned separately. Length of the slot is marked as datum C and has non diametrical TP 0.25 MMC, A, B MMC with the associated basic dimension of let say 4.5 mm in X direction (looking at the drawing length is in X and width is in Y). Width of the slot has also non diametrical TP 0.25 MMC, A, B MMC, C MMC with the associated basic dimension of let say 17 mm in Y direction. Both hole and the slot are on the same plane A . At some point insert stopped fitting so measurements started at both ends (our company and supplier). My results were showing TP out with center of the slot being only 3.7 mm in X and 17.15 in Y. Company which makes inserts admitted their punch was loose but said position is still in spec. I was setting alignment by measuring 2 radiuses of the slot, creating line between their centers and rotating alignment to it, they simply used 4.5 mm basic to create offset alignment which also automatically made 17.15 in Y shorter and almost perfect. They are also reporting TP of the slot's center in only one direction since in the other direction would be perfect based on the offset. I presented position in 2 directions (thanks to all the posts regarding generic features and variables), also tried explaining that TP callout is not only for the center but any point along slot's axis. I need some confirmation or correction to my method.
No, there's one way that it should be measured. You just don't seem to want to believe that you are wrong
Not exactly, I am opened to learn. Just don't understand why TP along the full length is not being checked but only in relation to center point. Since width is the shorter distance than length checking only TP of the width (along full axis) can show part as being good, when points at both ends of the length can still be outside +/- 0.125 and part simply will not fit where it supposed to. And that is exactly what happened in real life. Part fits on top of the pin where datum B is and slot fits on top of the diamond shaped pin where the slot is. At the same time outside profile of the part has to fit inside reverse profile. At some point one of the 2 cavities stamped by the supplier stopped fitting, but measuring with the offset alignment and checking only TP along the width shows part as good even though supplier admitted that the punch was loose.
No, there's one way that it should be measured. You just don't seem to want to believe that you are wrong
Not exactly, I am opened to learn. Just don't understand why TP along the full length is not being checked but only in relation to center point. Since width is the shorter distance than length checking only TP of the width (along full axis) can show part as being good, when points at both ends of the length can still be outside +/- 0.125 and part simply will not fit where it supposed to. And that is exactly what happened in real life. Part fits on top of the pin where datum B is and slot fits on top of the diamond shaped pin where the slot is. At the same time outside profile of the part has to fit inside reverse profile. At some point one of the 2 cavities stamped by the supplier stopped fitting, but measuring with the offset alignment and checking only TP along the width shows part as good even though supplier admitted that the punch was loose.
