To add to our stash of M3 metrology, we decided to attach Faro buttons to the flange where the M3 cell bolts on to the rest of the SAC cage. Since we'd used up all the invar buttons we had, it was time for a change of style - enter "the peanut-clusters"!
Each is a set of 3 ball bearings, epoxied so as to provide a location point for the Faro probe. 5 pairs of these buttons were then glued to the top & bottom of the flange (within reach of the Faro when it's stationed on its lower base) & held in place by piranha clamps while the epoxy cured.
In its usual position, the Faro's attached to the same ring as the SAC & so there's no problem of relative movement between the 2. However, when the Faro's down on its lower base (to reach the bottom end of the SAC), everything has to be Very solidly locked down. Ockert to the rescue with some extremely beefy bottle screws, nothing floppy about this design!