Tap Terminology: For Light Fixture Threaded Tube

[MrWhoopee]

Taper threads came first.

A Brief History of Pipe Threads

https://ultimheat.com/s3-museum/2019%20History%20of%20threaded%20pipe%20connections%2020190221.pdf

[nickel-city-fab]

I dunno, I really don't. Audel's mentions that the Briggs standard went all the way back to the 1860's but it also mentions straight threads.
I would guess that it all depends on when local building codes were developed. Roughly at the same time as the ASME.
I was trained for ASME work in welding and fabrication --
did you know they were originally sponsored by the Hartford Boiler Insurance Company?
Back in the days of steam.

So I wonder what came first.... Tapered pipe thread or straight pipe thread.

-D

[MrWhoopee]

Interesting story. I am surprised that the gas would have piped with straight threaded pipe and fixtures. It seems that tapered threads would have been a lot better, a lot easier to effectively seal against leaks. And even the expansion of the abbreviation (NPSM = National Pipe Straight Mechanical) speaks to the thread being used for MECHANICAL purposes, not for pipes carrying a liquid or a gas.

But then, strange things do and did happen.

I'm fairly sure they were NPT (tapered) when used to plumb gas but transitioned to straight when adapting fixtures to electric. It's pretty easy to just keep turning the NPT die to produce a straight thread, I've done it. Not sure it would meet NPSM specs, but it would hold a lamp together.

[Doozer]

So I wonder what came first.... Tapered pipe thread or straight pipe thread.
I mean, what came into usage to supply gas in homes. Straight thread fittings
or tapered thread fittings.? I know British have parallel (straight) pipe fittings
and they still use them today for gas and liquid. You can buy pneumatics
system components with parallel British pipe threads even today.


-D

[nickel-city-fab]

Perhaps the piping was re-threaded to suit? I have been (re)reading the 1921 Audel's Guides, and in it they state that the "Briggs" thread (now known as NPT) is the standard in the United States for all liquids and gases at ordinary pressures. They also give some pretty good recipies for pipe dope, and carefully distinguish between genuine wrought iron pipe and the new steel pipe.

Interesting story. I am surprised that the gas would have piped with straight threaded pipe and fixtures. It seems that tapered threads would have been a lot better, a lot easier to effectively seal against leaks. And even the expansion of the abbreviation (NPSM = National Pipe Straight Mechanical) speaks to the thread being used for MECHANICAL purposes, not for pipes carrying a liquid or a gas.

But then, strange things do and did happen.

[Paul Alciatore]

Interesting story. I am surprised that the gas would have piped with straight threaded pipe and fixtures. It seems that tapered threads would have been a lot better, a lot easier to effectively seal against leaks. And even the expansion of the abbreviation (NPSM = National Pipe Straight Mechanical) speaks to the thread being used for MECHANICAL purposes, not for pipes carrying a liquid or a gas.

But then, strange things do and did happen.

This is what I read somewhere, that the early electric lamps were wired up through the previous gas lamp piping, and the lamp threading standard just never deviated.

[gmax137]

National Pipe Straight for mechanical joints . Its use in lighting originated with gas lighting fixtures using 1/8 NPT, then carried over with the transition to electric.

This is what I read somewhere, that the early electric lamps were wired up through the previous gas lamp piping, and the lamp threading standard just never deviated.

[reggie_obe]

Too pooped out to think now
I was all morning doing yard work for an older church lady
her yard hasn't been touched in 20 yrs
the trees were lifting her roof off.

Thank you for leading by example.
A++, kudos, bless you, a mitzvah, good deed done, etc.

[nickel-city-fab]

Heaven help you when you're repairing an old industrial Singer machine and the screw disappears into the abyss. Not only do they have a unique pitch, but often an unusual head as well.
Not hard to make by the tens of thousands if you have a B&S auto screw machine.

Yep, and also so many other things had odd screws back in the day.
Like cars, phones, radios, typewriters, etc.
When I wake up or maybe tomorrow I'll try to get a pic.
The tap sets turn up on eBay all the time, cheap.
Too pooped out to think now
I was all morning doing yard work for an older church lady
her yard hasn't been touched in 20 yrs
the trees were lifting her roof off.

[wmgeorge]

Dozer has it right its NPT 1/8 inch, its really a no taper thread for electrical but it looks like a job for a 3D printer. Get the size close and will make / cut its own threads as you turn it on.

[reggie_obe]

Actually yes they do -- Thanks for posting that chart! I have not seen it before. Mine are all marked with the fraction size and TPI. The set was made by Greenfield. They have some really weird fractions in there, like 9/64-40 and 48.
5/32-36 and just odd stuff like that. I have to actually get the set out and have a look to find the actual numbers.
Only reason I got it was out of curiosity, and just in case I have to fix something really old.

Heaven help you when you're repairing an old industrial Singer machine and the screw disappears into the abyss. Not only do they have a unique pitch, but often an unusual head as well.
Not hard to make by the tens of thousands if you have a B&S auto screw machine.

[nickel-city-fab]

I may have posted this link before. Do the numbers on any of your taps match up with the SiManCo #s in the table?
https://www.singersewinginfo.co.uk/screw_threads

Actually yes they do -- Thanks for posting that chart! I have not seen it before. Mine are all marked with the fraction size and TPI. The set was made by Greenfield. They have some really weird fractions in there, like 9/64-40 and 48.
5/32-36 and just odd stuff like that. I have to actually get the set out and have a look to find the actual numbers.
Only reason I got it was out of curiosity, and just in case I have to fix something really old.

[MrWhoopee]

National Pipe Straight for mechanical joints . Its use in lighting originated with gas lighting fixtures using 1/8 NPT, then carried over with the transition to electric.

[reggie_obe]

It was made by Greenfield, yep they were sold to sewing machine repairmen. You can tell by the way the taps are marked, and its real oddball/ bastard sizes, Singer still uses some of them. The sizes are *nothing* like the modern machine screw sizes.I'll get a pic later if I can, too pooped out right now.
Turns out that Ma Bell also had their own special taps made, for phone work. Pre-war, so somewhere between 1890 and 1935 roughly.

I may have posted this link before. Do the numbers on any of your taps match up with the SiManCo #s in the table?

https://www.singersewinginfo.co.uk/screw_threads

[nickel-city-fab]

Sets? I've never come across any Singer taps. Was it something sold to machine repair people or? How are the taps marked? Please post an image of a set please.

It was made by Greenfield, yep they were sold to sewing machine repairmen. You can tell by the way the taps are marked, and its real oddball/ bastard sizes, Singer still uses some of them. The sizes are *nothing* like the modern machine screw sizes.I'll get a pic later if I can, too pooped out right now.
Turns out that Ma Bell also had their own special taps made, for phone work. Pre-war, so somewhere between 1890 and 1935 roughly.