I have a round block of material 150mm in diameter and 12.5mm thick. In the center of this block (on the Ø150mm surface)is a 45mm thru-hole (making it look like a doughnut). There is also an 8mm thru-hole that lies (radially) 40mm from center the 45mm hole. The primary datum is the top surface of the block, the secondary alignment datum is a line running thru both the 45mm and the 8mm holes. The tertiary datum is the 45mm hole. There also exists a 7mm hole that has the following locational dimensions: x=50, y=0, and "true position"/Ø 0.1

Since the callout for location of the hole is RFS, can a function gage be built that will check this hole position??

I seem to recall, from a class or something, that when the print calls for RFS location of a hole, a proper "function gage" cannot be made, but I cannot remember why not. I need an easy explanation.