I'm having trouble understanding how a bonus tolerance is applied when the MMC modifier is not on the feature itself, but on the tertiary datum in the FCF. I have a rough sketch and the report below. I get how the bonus tolerance works when the modifier is on the feature being positioned, but that's not the case here. I have two equally sized holes, one of them being Datum C. It gets no bonus. The other hole has a MMC modifier placed on Datum C in the FCF. Without that modifier, the hole position measures out of tolerance. But with it, it's within tolerance. But the way I thought I understood it, the hole should NOT be within positional tolerance because the size tolerance of Datum C is only +/- 0.02. With Datum C measuring 12.592, I should only get a bonus of 0.019. That would not be enough to put the hole being measured within tolerance. Yet, it shows up in tolerance on the report. So I guess I don't understand how the bonus is being applied here. I also don't get why Datum C is reporting out of tolerance at the very bottom. One last thing, I don't understand what that S modifier is supposed to do. I thought it was an outdated modifier for Regardless of Feature Size, which is assumed anyway, so I don't get its purpose here or what it does when adding it to the FCF. It doesn't appear to change anything when I take it out. I'll take any advice I can get, though I have a feeling most of it will run over my head right now. Thanks.
That's how the software is applying the allowable bonus from the C datum, before it reports your deviation. It's not a case of just adding it to the tolerance in the feature control frame when the MMC symbol is on a datum it's called MMB on the feature itself it's MMC. MMC gets added, MMB gets a datum shift, rotation about the primary datum in this case.
Ok thanks, I guess I haven't learned about that yet. Does anyone happen to know if this is covered in the Hexagon PC DMIS GD&T course? I'm taking that in November. I'm hoping that will answer some of the questions I have about the various items the report spits out when I add position dimensions.
