Just came across a print with a feature control frame that puzzled me. I'll do my best to describe it here and my question that follows. The feature control frame is a true position callout to three datums. The first is datum F, a plane. The second, and the one that stumped me is a combined datum of two slot features (S & T). The third is a combined datum of two circles (K & P). Below is how the feature control frame looked on the print.
Position
| 0.005(M)
| F
| S(M) - T(M)
| K(M) - P(M)
The way I interpret the secondary datum
|S(M) - T(M) was by combining both the individual "S" & "T" datum slots into one slot feature labeled as datum S-T. The feature control frame appears to be asking to apply max material to both the individual "S" & "T" datums though, and not to the new combined S-T datum. The new secondary datum would control the rotation by sending an axis through both slots since they live on the same axis line.
The third datum
| K(M) - P(M) would be the combinate of two "K" - "P" circles into a line perpendicular to the "S-T" datum. If the new third datum is another axis line that is constructed of two circles that are perpendicular to the secondary datum, how would you apply max material to them as shown in the feature control frame?
The print lists all the datums individually on the print.
F=plane
S=slot
T=slot
K=circle
P=circle
The way the feature control frame on the print appears to combine "S" & "T" into one datum, and "K" & "P" into another datum. The feature control frame appears to be asking to apply max material to the new combined datums, but max material to both the features used and not to just the new feature.
My overall question is this. How do I build this feature control frame into PC-DMIS to recognize this specific callout and apply the max material as it is intended?
