I'm working on a 5" dia. pressure gauge with broken glass. I've purchased a piece of 1/8" glass cut to size. Now it's time to figure out how best to mount the glass in the gauge.

This gauge did not have any gasket material between the bezel and glass, or between the glass and body. This gauge does not have a glass retaining ring to hold the glass into the bezel.

What material would you suggest for use as a gasket when installing a new piece of glass in a pressure gauge? Would you use gasket material on both faces of the glass? If just one, which face? Or perhaps a gasket material which wraps around the edge of the glass?

Suggestions are appreciated.

Regards,
Bob Milhaupt
Steam Department Volunteer
Illinois Railway Museum

Ordinary card stock works fine, but I prefer 1/32" sheet cork for locations that get wet repeatedly. Last order of sheet cork I purchased from McMaster Carr. I prefer a gasket on each side of the glass, for protection from vibration and or a high spot on the case or retainer, if there is sufficient clearance. I typically will attach the gaskets to the face of the glass with a very small amount of silicon caulk. I am fortunate to have a circular gasket cutter that works well thin gasket materials, but they can be cut out quite easily with scissors.

Mike Tillger

Hi,

You've got many options, including just installing the new glass the way the old disk was installed. Another option would be to run a slight bead of clear silicone caulk, (using a small tube of bathroom caulk) around the seating surface of the bezel. Just plop the glass in and let the caulk dry, then trim any that has oozed out with a razor blade. This will keep the glass from rattling and keep water and dust out. You could also add a thin card gasket inside the glass to make the gauge totally dustproof, but the silicone is really enough. Most locomotive gauges have threaded bezels and a good way to break your glass is to turn them onto the case with a lot of torque. When the bezel stops turning, don't force it further. If you really want to go old school, use glazier's putty between the glass and the bezel, screw everything together and wait for it to dry. More trouble than it's worth, maybe. If this is a steam gauge, consider drilling a 3/8 or larger hole in the back of the case and placing a rubber plug in it. In the unlikely event that a bourdon tube fails, the steam will blow out this safety plug instead of pressurizing the gauge and exploding the front glass. Many end-of-steam era main gauges had such blow out plugs.

That's relatively new....white lead and oil would be the real historical fix. Glazers putty replaced it.

dave

A gasket made from regular old window putty would be indistinguishable from one made with white lead putty, except the latter would eventually produce poisonous dust. The old white lead putties intended for holding glass in place were mostly glazier's putty anyway, something like 10% lead, 10% linseed oil. I can't imagine pure white lead and oil forming an effective gasket without a putty binder.

It goes on like a syrup but hardens nicely over time and temperature. Don't ask me how I know.

dave