Hi Bill, you might consider using clear acrylic sheet turned to size. Look at the image below: one of the 10ths indicators has a real crystal glass, the other one is plastic.
And close-ups:
Yes, the one on the left (or the top close-up) has the fake glass.
The ”smudge” below the “No. 77” is from a former owner’s finger print - they kept using the indicator with the glass gone before i acquired them. Got most of it off, but was not taking the chance to ruin the printing on the bezel by scrubbing harder...
There is a company in NJ that refurbishes these (and sells new ones), but it would have cost way more that I was willing to pay.
So...
I made a disc of aluminum (pressure disc) slightly larger than the OD of the glass. Relieved most of the center until only a thin strip at the outer edge was left (only about 20 thou deep). The back side had a center in it. I then turned and faced a piece of aluminum, also slightly larger in diameter than that of the glass. I then rough cut some acrylic with scissors oversized. (There are lots of different thicknesses available for purchase from hobby stores or even Home Depot, Lowes, Rona, etc.). This was then sandwiched between the turned and faced ”driver” and the “pressure disc”. The tailstock was used in the center of the pressure disc to apply sufficient pressure to keep the sandwich together for turning. Using sharp HSS tools, I turned the whole thing (Alu driver, acrylic sheet and Alu pressure disc) to the required OD to fit the indicator. After peeling the protective cover off the plastic and some light deburring to break the sharp edges, I had a perfectly good replacement for a US$200 piece of glass.
