Ever wonder about the weird threads on light fittings?

[oldbrownhat]

OK, maybe I'm the only one... Those little packages of threaded tubes and nuts etc. are pricey. Turns out the specs on those things go back to the 19th c when gas was used for lighting. They're IPS (Iron Pipe Size / NPS (National Pipe Straight). When they went to electric light, the specs were already standardized by ASME so they just kept the outside dimensions and thread pitches and used thinner wall tube to allow wires to pass through.

What is IPS and Why Do We Use These Size Threads for Lighting Parts?​

Trivia post for the day. We now return you to your regular programming.

 

[swsig]

Ever wonder about the weird threads on light fittings?​

No.

 

[oldbrownhat]

Ever wonder about the weird threads on light fittings?​

No.

Well, I guess that settles it- maybe I AM the only one and just need to get out more

 

[glenwolde]

Yes I have. Now I know.

 

[oldbrownhat]

Yes I have. Now I know.

That's a relief. It can get lonely out here in Triviaville.

 

[03hemi]

I guess I'm one of them?

 

[dockmurgw]

Never wondered why...but as an electrician I had a bin full of them and other fixture mounting hardware in my van because you never knew when a part would come in handy.

 

[taz666]

If it weren't for different pipe/thread spec's we'd have people cobbling all sorts of stuff together.

 

[BLACKHAWKNJ]

When NYC built the IRT subway in 1904 all the light fittings had left hand threads so people couldn't take them home.

 

[NYlakesider]

When NYC built the IRT subway in 1904 all the light fittings had left hand threads so people couldn't take them home.

I worked for years at a huge construction site in Albany NY in the 60s & 70s. (South Mall) They had reverse thread bulbs and fixtures for much of the temporary lights. They wer just long strings of wire with bulb sockets attached to them ever 10' or so!

It was for the most part just a money waster as the more aggressive crooks took home both the wire & fixtures and bulbs. I can remember that as far as the late 1990s one person I knew was still lighting his garage with that system. A quick look showed at that time he still had about 200 lefty bulbs on a storage shelf!

 

[WR Moore]

I recall looking at an old farm house where the original hard installation indoor lighting was gas. When they went to electric, they just ran the wires through the pipes. Wonder if that's how it started? NO, we didn't buy the place. Back when they did that sort of thing, cloth was sometimes used for insulation. Didn't want to discover that (or whatever else they used as insulation) was still in the house, and there were enough other things that made keeping a neutral face difficult.

 

[Rustyt1953]

"Ever wonder about the weird threads on light fittings?"​

Put me down as a no.

 

[Krogen]

Well, I never did wonder about those weird threads. But now that I know the background, I'm interested. I always like to know "why." Evidently my first word wasn't MaMa or DaDa . . . It was "why." People who know me, aren't surprised.

So here's one for you @oldbrownhat . Who invented the wire nut? To my knowledge they weren't ever used in the knob & tube era but came in later. Why izzat?

 

[BC38]

I recall looking at an old farm house where the original hard installation indoor lighting was gas. When they went to electric, they just ran the wires through the pipes. Wonder if that's how it started? NO, we didn't buy the place. Back when they did that sort of thing, cloth was sometimes used for insulation. Didn't want to discover that (or whatever else they used as insulation) was still in the house, and there were enough other things that made keeping a neutral face difficult.

LOL, have you ever seen an early 20th-century structure with "knob & tube" wiring?
When I was working as a service manager for an electrical contractor I saw several of them.
Knob & tube was a wiring system of copper wires, with minimal (cloth) insulation, strung from one stud-mounted ceramic insulator to another, behind the lath & plaster walls of the structure.
In the early days of "electrification" of our country, knob & tube wiring was the standard, because it was the best technology available at the time.
By today's NEC standards, knob & tube wiring is basically an electrical fire just waiting to happen. But there are still quite a few old turn-of-the (last) century buildings out there that are wired that way.
Scary, but true....

 

[TX-Dennis]

I never really wondered about the threads on lighting. I just accepted that that's the way it is. but as Paul Harvey used to say, "Now you know the REST of the story."

 

[Engineer1911]

No, but I was a member of ASME for about 12 years.

 

[oldbrownhat]

LOL, have you ever seen an early 20th-century structure with "knob & tube" wiring?
When I was working as a service manager for an electrical contractor I saw several of them...

My original old house here, built about 1931 (if the dates on fragments of shredded newspapers I found in a wall were any indication) originally had w&t. All long since replaced but there were some insulators on a beam in the basement. wish I'd kept them as a souvenir before I had it torn down.

@Krogen, re wire nuts. I didn't know so had to look it up. I know them generically as "Marrettes" and, lo and behold, according to Wikipedia, invented in Canada:

William P. Marr emigrated from Scotland to Ontario, Canada early in the twentieth century. After settling in the Toronto area, he was employed as an electrician contractor for Ontario Hydro, converting gas-lit homes to electrical incandescent lighting...​

​

...Marr was injured when he spilled molten solder on himself. Seeking a safer, more efficient connection method, Marr, working in his home workshop, developed the first pressure-type wire connector. In 1914, he produced a set-screw version, the forerunner of the present-day twist-on connector used throughout North America.... Patented in 1926​

 

[Lance Boyle]

LOL, have you ever seen an early 20th-century structure with "knob & tube" wiring?
When I was working as a service manager for an electrical contractor I saw several of them.
Knob & tube was a wiring system of copper wires, with minimal (cloth) insulation, strung from one stud-mounted ceramic insulator to another, behind the lath & plaster walls of the structure.
In the early days of "electrification" of our country, knob & tube wiring was the standard, because it was the best technology available at the time.
By today's NEC standards, knob & tube wiring is basically an electrical fire just waiting to happen. But there are still quite a few old turn-of-the (last) century buildings out there that are wired that way.
Scary, but true....

lol, stayed at a seaside cottage in Maine with the family. I am laying in the upper bunk in one of the upstairs bedrooms and notice the knob and tube wiring going to the bare light bulb that was on……my eyes following it as it goes through the joists and I see a wire clothes hanger obviously hanging off the wiring. What the heck, the cloth insulation was half gone lol, may as well add unintentionally being the ground to the fire hazard.

 

[Krogen]

My original old house here, built about 1931 (if the dates on fragments of shredded newspapers I found in a wall were any indication) originally had w&t. All long since replaced but there were some insulators on a beam in the basement. wish I'd kept them as a souvenir before I had it torn down.

@Krogen, re wire nuts. I didn't know so had to look it up. I know them generically as "Marrettes" and, lo and behold, according to Wikipedia, invented in Canada:

William P. Marr emigrated from Scotland to Ontario, Canada early in the twentieth century. After settling in the Toronto area, he was employed as an electrician contractor for Ontario Hydro, converting gas-lit homes to electrical incandescent lighting...​

​

...Marr was injured when he spilled molten solder on himself. Seeking a safer, more efficient connection method, Marr, working in his home workshop, developed the first pressure-type wire connector. In 1914, he produced a set-screw version, the forerunner of the present-day twist-on connector used throughout North America.... Patented in 1926​

Very interesting. Thanks! First time I've heard "marrettes." I sure understand the concern about spilling molten solder. It's one reason I haven't taken up bullet casting. I've splattered enough on myself when soldering circuit boards to know it stings. But "spilling" implies a significantly larger amount, like the solder pot we used for tinning large cables or a casting furnace. Ouch.

Knob and tube appears dangerous but it isn't necessarily so. My ex and I had a 1940 house with knob and tube. The neighbor was a fire fighter and explained knob and tube is quite safe if it's in good condition and not abused or used as a clothesline. Our basement had exposed wiring in the upper floor's joists. I can see the temptation to hang stuff on it. The big thing about knob and tube is the large separation between hot and neutral. Of course that doesn't apply to fixtures, switches and the like. On top of that, there's no ground; just hot and neutral. No 3-prong outlets.

 

[oldbrownhat]

...The big thing about knob and tube is the large separation between hot and neutral...

Also true I believe of the power lines out at the road, which are several feet apart on the pole. Apparently there's up to 25,000V on those.