Threading on glass gauge nuts? (or are sight-glass related specs a secret?...)

Jim_NY

Been doing my own steam-boiler sight-glass cleaning/replacement for years. Just helped a neighbor do it for the first time. We both have 5/8ths glass.

Making conversation, he asked, "so what kind of threading is on these things" (the glass gauge nuts). Other than that it's "standard" - never thought about it. And even though I know it doesn't matter, unfortunately now I'm curious.

My best-est web-search terms couldn't find anything. A couple of tries at online customer service of suppliers accessible to non-professionals, only got back "it's standard."

With my bad eyes, looks like near to ~20 TPI, with a ruler near to ~7/8" - and since it uses a gasket, may be straight thread...?

It would be too much of a coincidence if it turned out to be the kitchen-faucet aerator "standard" (which one website said is 15/16"M 55/64"F -20 UN thread). But would guess it's at least close.

Thanks.

EBEBRATT-Ed

I don't know what thread it is but it's one of those "who cares" thing. They are all the same as far as I know unless you get on high pressure steam.

Google: Ernst instruments

mattmia2

us a micrometer or a caliper. use a magnifying glass and measure several threads and divide for the pitch. what profile are they?

hot_rod

I believe it is the same thread as most other 5/8” compression fittings. It uses a rubber ring instead of the brass ferrule, on glass tube

Jim_NY

Thanks for giving it a shot. I have no experience with this sort of thing (determining TPI and pitch etc.), and don't have the tools to get a precise measurement. Couldn't quickly find the specs for other compression fittings, as reasonable suggested.

I'll just have to try to sleep at night : )

Mad Dog_2

Never pondered it, but there are so many different thread patterns we work with. Mad Dog

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1817442#Comment_1817442

Including 100% custom ones.

Sootmaster

Super Dooper tap and die kit should have a thread guage in it. Kind of like a set of feeler guages but they have little teeth that nest into the threads to tell you what the pitch is.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1817495#Comment_1817495

Kinda like this

Jim_NY

ChrisJ said: Kinda like this. [photo]

Whoa. That's a beautiful vintage tool. Wish things were still made like that.

Seeing that Made-In-USA gauge inspired me to give it one last web-try before shutting-down, and I'll be darned. Found something in the Q&A for a 5/8" glass Conbraco nut at MSCDirect:

Q. Asked by Ethan 5 years ago: What is the inside threading of this nut?
A. Staff Expert - Rob: The thread size on this nut is 15/16-18 tpi

mattmia2

https://www.grainger.com/product/STARRETT-Thread-Pitch-Gauge-Set-Metric-2ZVE2

Jim_NY

mattmia2 said: link to Gauge Set at Grainger

Made me smile. I was picturing something more like an $8.99 set at Amazon…

mattmia2

it looks like general only makes the style like i have now that is like a set of feeler gauges but hinged at both ends with different ranges at each end but starrett still makes the triangular style

PC7060

https://forum.heatinghelp.com/discussion/comment/1817507#Comment_1817507

I’m very curious about the sketch on the reverse side on the paper in the picture. 😂

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1817692#Comment_1817692

I think it was a very crude fast drawing of a check valve and pressure relief.