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.
Thank you. Except your graphics are based on slot actually located at 4.5, -17. If the slot is at 3.7, -17.15 when squared, than after rotating to 4.5 offset line it will be skewed in relation to the rest of the assembly and this part will never pass hard gauge which would be: one pin simulating B at MMC of the hole and another pin with the shape of the slot and size of L (MMC) - 0.25, W (MMC) - 0.25. There is only 0.02 bonus from B and size of the slot is only bigger than it's MMC by 0.02 in L and 0.02 in W. Centers of the 2 pins would be at exact basic distances from the drawing.
I suppose there's a question we've overlooked. What is master? The print, or CAD?
If the print is master, then:
The slot
can't be 3.7 in the X direction. The print defines the location of the slot in the locating direction as 4.5. Not the other way around.
If your gage is built with a slot shaped locator,
it's wrong. The GD&T defines a DRF which rotates to the major axis of the slot. It should be a two-way locator in the length axis.
If CAD is master, then:
The slot
still can't be at 3.7 in the X direction, because, again, the location of the slot in the alignment direction is defined, not by the part, but by the GD&T. So, it would be at whatever it shows to be in CAD.
Thank you. Except your graphics are based on slot actually located at 4.5, -17. If the slot is at 3.7, -17.15 when squared, than after rotating to 4.5 offset line it will be skewed in relation to the rest of the assembly and this part will never pass hard gauge which would be: one pin simulating B at MMC of the hole and another pin with the shape of the slot and size of L (MMC) - 0.25, W (MMC) - 0.25. There is only 0.02 bonus from B and size of the slot is only bigger than it's MMC by 0.02 in L and 0.02 in W. Centers of the 2 pins would be at exact basic distances from the drawing.
I suppose there's a question we've overlooked. What is master? The print, or CAD?
If the print is master, then:
The slot
can't be 3.7 in the X direction. The print defines the location of the slot in the locating direction as 4.5. Not the other way around.
If your gage is built with a slot shaped locator,
it's wrong. The GD&T defines a DRF which rotates to the major axis of the slot. It should be a two-way locator in the length axis.
If CAD is master, then:
The slot
still can't be at 3.7 in the X direction, because, again, the location of the slot in the alignment direction is defined, not by the part, but by the GD&T. So, it would be at whatever it shows to be in CAD.
