This will be a challenge because the MDR machine uses adjustable needle bearings on the trunnion assembly, so there is no shaft on which to mount the potentiometer.

First, in order to be able to mount the digital meter and housing close to the frame, we must do something about the conical set screw and big acorn jam nut. We will replace it with a short 5/16-18 set screw and ball bearing. The ball bearing securely fits the drilling which used the conical point. In this way, we can preserve all the original parts.

Now in order to replace the function of the jam nut, a short set screw is installed over the one bearing the ball. This can then be seated against the first screw, to securely lock the adjustment, just as the jam nut did. We now have a flush surface which will interfere less with mounting the potentiometer and DPM housing.

A shaft clamp is made for the potentiometer shaft. A dowel pin will mechanically couple it to the quill. The shaft is accurately located on the bearing drilling with a center drill and the matching dowel location transferred.

The pin is fitted.

Another clamp is made…