Just thought I'd share yet another approach to sight glass assembly. Very happy with how they turned out. This is on '43 10EE round dial, but I expect will translate to other machines.
Here's the stackup of parts. O-rings to seal - no goo required. Careful not to over tighten (glass doesn't like it)
Glass - 23.9mm x 2.0mm watch crystal (e.g. 2.0mm Flat Round Mineral Glass Crystal (17.0mm-35.0mm / 0.1m )
O-rings - Square profile Buna-N -019 13/16" ID, 15/16" OD, 1/16" Cross Section (e.g. McMaster-Carr )
White backplate - 3D printed in white PLA. Let me know if anyone wants STL file. 3 ears around the perimeter help retain it into the housing during assembly. The ears are slightly oversized vs. my housings and I individually trimmed them with x-acto knife for best fit into each housing. Raised ridge on the backside keeps back o-ring in place. This way it all stays together as one assembly as it is put in place.
Here's the stackup of parts. O-rings to seal - no goo required. Careful not to over tighten (glass doesn't like it)
Glass - 23.9mm x 2.0mm watch crystal (e.g. 2.0mm Flat Round Mineral Glass Crystal (17.0mm-35.0mm / 0.1m )
O-rings - Square profile Buna-N -019 13/16" ID, 15/16" OD, 1/16" Cross Section (e.g. McMaster-Carr )
White backplate - 3D printed in white PLA. Let me know if anyone wants STL file. 3 ears around the perimeter help retain it into the housing during assembly. The ears are slightly oversized vs. my housings and I individually trimmed them with x-acto knife for best fit into each housing. Raised ridge on the backside keeps back o-ring in place. This way it all stays together as one assembly as it is put in place.