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pmarc, I see but, I think that on the other hand there is this logic: MMC (the tolerance modifier) invokes the virtual condition as the limiting boundary for the feature being controlled. MMB (the datum reference modifier) invokes the virtual condition of the datum feature as the datum feature...

Not sure if you mean the same thing I'm about to say, but: CIrcled M after the tolerance value in the FCF means a tolerance at MMC and yes, the bonus depends on geometry, but more precisely on the size (diameter or width) of the cylinder or tab/slot being considered. The larger a hole or the...

Modifying tolerances to apply at MMC and datum features applied at MMB allow to make inspection simpler than when not using the circled M symbol. If the symbol is not used, then a tolerance applies regardless feature size and you have to measure the theoretical axis or center plane, or a derived...

April fools jokes aside, It seems to be common to refer to the use of geometric characteristic symbols placed in feature control frames as GD&T (yes, "Geometric" Dimensioning and Tolerancing). Training materials seem to suggest that there is either a "traditional" method in which all tolerances...

What's the problem with the term GD&T? It has been standardized for many years now to mean General Dimensioning and Tolerancing. Thinking that "G" stands for Geometric is as outdated as referring to a Position Tolerance as True Position.

Lots of dimensions and a lot of them can't be evaluated reliably if the general +/-0.1 from the note applies to them. Now you have no choice but delete the +/-0.1, write UNTOLERANCED DIMENSIONS ARE TED, and specify a general surface profile relative to the main datum system (A,B,C ?).

greenimi, The function of MMC position is to allow clearance fit with a feature that is fixed in a mating part that interfaces with the datum features. The function of RFS position is to locate a mating component. In the standard example the function of the 8 dia. mm hole could be to clear a pin...

So, you are asking about RMB (the datum feature material boundary modifier), not about RFS (for the mutually locating position tolerance specification). ASME Y14.5-2018 states: " 7.12.4 Pattern of Features of Size RMB When RMB is applicable in a feature control frame to common datum features...

greenimi, RFS would be interpretable. In terms of the requirement it's two dia. 0.15 mm coaxial cylindrical tol. zones in which the two unrelated actual mating envelope axes must fit. In terms of the measurement It's two measured zones fitted over the two unrelated measured mating envelope axes.

mfgenggear, Yes, I'm not sure why there is the basic dia. 39, maybe OP was thinking to control it with a general profile? Anyway I'd simply specify a larger direct tolerance as in my above suggestion in post #7 (+/-.xxx where .xxx is just loose enough to still not cause any trouble).

Limited length or area dimensions are a lot like datum target area dimensions. You don't control their variation on the part drawing that uses them, but that's also why you should specify them as basic ("theoretically exact") - you assume that they are exact and someone's job is to make sure...

I'd probably do something like that:

Or as shown in these examples... The first one is the same as using a Continuous Feature modifier for the 35+/-0.1 diameter.

Season, In the second case, there is no control over how off-coaxial the two ends can be. Here is an exaggerated illustration.

Tolerances for the fixture design should be about 1/10 of the tolerances being verified by the fixture.

greenimi, A cylindricity tolerance zone, whether per unit length or full length, is always 2 coaxial cylinders. Suppose a measured zone that is as long as the full length of the actual cylinder is best fitted over the actual 100 mm long cylinder and it should measure up to 0.4 mm. Then a 10 mm...

mfgenggear, I think there could be a go gage fixture as 3DDave described: two recesses of diameter 20.53 and a saddle of diameter 23.1, following the sections and bends of the tubing. I suppose it's not a cheap fixture, but if enough parts are to be manufactured, it should be worth the...

As 3DDave mentioned, most of those requirements can be verified with a functional go gage. That is because datum reference A(M)-B(M) is specified at MMB, and the positional tolerances referencing it apply at MMC.

If you delete the datum feature qualifying feature control frames, your datum features A and B will be left uncontrolled other than for size. If you keep those controls, the datum features A and B are controlled relative to a datum reference frame with all 6 degrees of freedom locked, so their...

Why not establish a datum reference frame from datum features or datum targets and then apply simultaneous profile requirements to the left flat surface and to the right conical end of the hole. Also, a positional tolerance for the interrupted hole in the same DRF. Then do the tolerance stack to...