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lenses in old gas regulators

Cut a round, use a pitch dop to fix in a three jaw and bevel ( gently) with a diamond whetstone, goes quick actually, I’ve made little windows for some lab equipment this way, it’s doable.
There’s a non reflective picture glass about right for old gauges and clock glasses, plus watch glasses are available too, convex glass.
Lab suppliers list them by the score up to 6-8” if you like
Mark
 
Any gas for which there is a detector there must be a calibration/check gas. And then there is CNG.

Kinda funny they mentioned NG and Methane, most folks wouldn't bother with the difference.
Semiconducter industry uses Methane in some plasma system operations. It would be UHP, unlike the natural gas.
 
Cut a round, use a pitch dop to fix in a three jaw and bevel ( gently) with a diamond whetstone, goes quick actually, I’ve made little windows for some lab equipment this way, it’s doable.
There’s a non reflective picture glass about right for old gauges and clock glasses, plus watch glasses are available too, convex glass.
Lab suppliers list them by the score up to 6-8” if you like
Mark
You sound very knowledgeable and are probably way more experienced than I am. As I understand it, dopping an item onto a stick (or round bar with flat end) whether with wax, pitch, CA glue or even epoxy glue is basically gluing your piece onto said stick. So how do you do this exactly in the middle? If you don't get it right in the center you'd have horrific runout when you tried to bevel the part.

metalmagpie
 
For 2" lenses for your gauges
use the 2" clear glass lenses from welding goggles.
I thought everyone knew that.

-Doozer

That's actually a great idea. But these are 2-1/2" gauges, not 2", and welding goggles don't come in 2-1/2". Something about then they'd be too far outside your pupils. I also looked at flashlight lenses. That seemed promising until I realized they were cut from superthin glass, and I need 3/16" thick.
 
Once you have new covers, remove and check that the gauges work properly. I find gauges with broken covers are rarely, if ever, still accurate.
If the needle goes correctly to zero, and putting a little pressure on it swings the needle smoothly up to some low value, and putting more on makes it go farther smoothly, and letting off the pressure causes the needle to move smoothly back to the zero pin, as far as I'm concerned that gauge is certified by the National Bureau of Standards. Broken gauges don't move, or they don't move right. And they don't come in mint brass cans either.
 
You sound very knowledgeable and are probably way more experienced than I am. As I understand it, dopping an item onto a stick (or round bar with flat end) whether with wax, pitch, CA glue or even epoxy glue is basically gluing your piece onto said stick. So how do you do this exactly in the middle? If you don't get it right in the center you'd have horrific runout when you tried to bevel the part.

metalmagpie

1. Use hand pressure and hold the tool like a file so it follows the part. Think more like lapping where the system is compliant. Less like grinding where everything is rigid.
2. Set tru or independent 4 jaw.
 
As you cut the circle of glass, snap it out, dip the end of a bit of brush handle in melted pitch, then stick it in the lathe Chuck.
Press the disk as close as possible onto the dop ( warming with a cook torch might be needed, Back that up with the tailstock, I used a cork with a hole or bung as they are all over the place in a lab.
It doesn’t matter if it perfectly centred as the diamond file will follow the edge.
Lathe on slowest speed btw!.
Sometimes it’s too wobbly so refix it , warming required
A glue gun dop works too, easier to release the glass, squirt of isopropanol or iso propyl alchohol works.
With glass I found slow.
Mark
 
Semiconducter industry uses Methane in some plasma system operations. It would be UHP, unlike the natural gas.
Interesting, thanks. I'm not sure how pure we can get in our facilities, but I doubt it would meet a UHP spec. We do have one plant that makes some damn fine propane, it almost all meets high purity spec with no real effort. Gotta be a combination of a good process and ideal feedstock.
 
trepan your own lenses out of sheet on a lathe (stick the plexi down to a backer with double sided tape), then bevel. Polish (still on lathe) with various grit paper then "flame polish" (way easier than it sounds).
 
I would stick with plastic / plexiglass for 'homemade' lenses. Remember you have high pressure gas in those gauges. If the bourdon tube ruptures, I would worry that regular window glass (annealed flat glass) could turn into high velocity razor sharp splinters flying through your shop. I assume modern gauge lenses are tempered safety glass that crumbes into round pieces when broken or the gauge lenses are plastic.

I the 'good old days' the regulator manufacturers used regular annealed flat glass, but I assume that in the last fifty years their insurance carriers got tired of paying for eyes and made them change the material.
 
If the needle goes correctly to zero, and putting a little pressure on it swings the needle smoothly up to some low value, and putting more on makes it go farther smoothly, and letting off the pressure causes the needle to move smoothly back to the zero pin, as far as I'm concerned that gauge is certified by the National Bureau of Standards. Broken gauges don't move, or they don't move right. And they don't come in mint brass cans either.
A backplate that is angled forward will interfere with the needle near the middle of travel.
 








 
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