Measuring Threaded Female Things

[TromboneAl]

Hey, don't blame me for the provocative thread title. It's appropriate!

While installing our new range, I made a wasted trip to the hardware store, and this is why:

I measured the gas input threaded female "port" and determined that it was larger than half-inch:

Turns out, it did indeed mate with a half-inch adapter. Perhaps "half-inch" refers to the inner diameter?

 

[rayinpenn]

Click bait alert!

 

[NW-Bound]

WARNING: Things are often smaller than they appear to be.

 

[brewer12345]

I run into this all the time with reloading stuff, where a difference if a thousandth of an inch can make a real difference. A pair of digital calipers can help a lot.

 

[candrew]

Hmmm.....only another half-inch?

 

[CardsFan]

Actually, in the case of pipe size, the stated size is "nominal". Depending on the pipe size and wall thickness it may not match either the inside or outside diameter. In smaller size pipe, the OD is always greater than the nominal size.

 

[Sunset]

Well I'm disappointed I clicked on this thread

 

[braumeister]

Size matters.

 

[Jerry1]

Actually, in the case of pipe size, the stated size is "nominal". Depending on the pipe size and wall thickness it may not match either the inside or outside diameter. In smaller size pipe, the OD is always greater than the nominal size.

So how do you get the right size from the store? Buy various sizes and return the ones that don't work? I agree with OP, That doesn't look like 1/2 inch. I would have bought 3/4.

 

[ArkTinkerer]

Pipe is done by the inside diameter. But even then you have different thread types and fine vs coarse. For nuts and bolts you can get a plastic template or something like a giant keyring with small threaded segments/nuts to test the real part to know what the thread is. Never seen that for pipe before but you could make a test board like they often have in the plumbing sections of the hardware store.

 

[Just_Steve]

So how do you get the right size from the store? Buy various sizes and return the ones that don't work? I agree with OP, That doesn't look like 1/2 inch. I would have bought 3/4.

^This^

 

[ERD50]

Pipe is done by the inside diameter. .....

ding-ding-ding - winner!

I too was confused about this for a long time, until you realize that the way they do it makes perfect sense. If you have a 1/2" pipe, you never want the flow cross-section diameter to go below 1/2". So the threaded parts associated with 1/2" pipe will always be quite a bit larger than 1/2". They need to account for wall size, threads, etc.

And that carries over to non-threaded adapters ("couplers") for copper pipe for example - the coupler's ID will be a fit to the OD of the copper pipe. If the coupler fit on the inside, it would restrict the pipe to less than 1/2".

And earlier it was mentioned these are nominal sizes, I think generally 1/2" is just a bit larger, to allow for tolerances and still not be < 1/2" (or whatever size you are dealing with).

Solid metal rods and "tubing" (versus pipe) are the opposite - the OD is what matters, and they might spec a wall thickness (which in turn sets the ID).

So, specific to the OP picture/question: "Turns out, it did indeed mate with a half-inch adapter. Perhaps "half-inch" refers to the inner diameter? " Yes, the ID of the male part should be ~ 1/2", so female ID needs to be large enough to accommodate all the wall thickness I mentioned. Is that what you found?


-ERD50

 

[mystang52]

My easily successful DIY jobs are far outnumbered by the multiple-attempts jobs. To try to minimize the latter, I learned one thing a long time ago. To wit, despite my best good faith measurement efforts, I buy different sizes and later return the ones that don't fit.
BTW, loved the thread title.

 

[CardsFan]

ding-ding-ding - winner!

I too was confused about this for a long time, until you realize that the way they do it makes perfect sense. If you have a 1/2" pipe, you never want the flow cross-section diameter to go below 1/2". So the threaded parts associated with 1/2" pipe will always be quite a bit larger than 1/2". They need to account for wall size, threads, etc.

And that carries over to non-threaded adapters ("couplers") for copper pipe for example - the coupler's ID will be a fit to the OD of the copper pipe. If the coupler fit on the inside, it would restrict the pipe to less than 1/2".

And earlier it was mentioned these are nominal sizes, I think generally 1/2" is just a bit larger, to allow for tolerances and still not be < 1/2" (or whatever size you are dealing with).

Solid metal rods and "tubing" (versus pipe) are the opposite - the OD is what matters, and they might spec a wall thickness (which in turn sets the ID).

So, specific to the OP picture/question: "Turns out, it did indeed mate with a half-inch adapter. Perhaps "half-inch" refers to the inner diameter? " Yes, the ID of the male part should be ~ 1/2", so female ID needs to be large enough to accommodate all the wall thickness I mentioned. Is that what you found?


-ERD50

Here is a handy chart, showing OD, ID, and thread count for various sizes of standard wall (schedule 40) NPT (National Pipe Thread) pipe
https://www.engineeringtoolbox.com/ansi-steel-pipes-d_305.html

This one shows the variation in wall thickness and ID, depending on the schedule
http://www.tiogapipe.com/assets/files/pipe-chart.pdf

For each size pipe, the OD is constant. Only the ID and wall thickness vary based on the pressure rating.

 

[JoeWras]

I'm more confused by Al's ruler than the problem at hand. Never seen one like that!

 

[Happyras]

I'm more confused by Al's ruler than the problem at hand. Never seen one like that!

I am more afraid with him doing gas piping not knowing pipe sizing or thread style. If he uses a flare adaptor thinking its a pipe thread, it will leak. Yikes!

 

[RobbieB]

Yeah, it's internal pipe size. The OD of a half inch pipe is bigger than three quarters.

 

[Curmudgeon]

I am more afraid with him doing gas piping not knowing pipe sizing or thread style. If he uses a flare adaptor thinking its a pipe thread, it will leak. Yikes!

+1, with all due respect!

Are you using pipe dope? Is it dope or tape specifically approved for gas?

 

[mickeyd]

This thread indicates why plumbers have secure jobs.

 

[MichaelB]

A thread about threading threads?

 

[GalaxyBoy]

A thread about threading threads?

 

[CardsFan]

A thread about threading threads?

At least you mods don't need to worry about this one turning political!

And BTW. Thank you for keeping this a sane place to visit.

 

[harley]

At least you mods don't need to worry about this one turning political!

And BTW. Thank you for keeping this a sane place to visit.

I'll buy safe, but sane may be stretching it.

 

[ERD50]

At least you mods don't need to worry about this one turning political! ...

You do realize there are LEFT and RIGHT hand threads don't you?

And PEX tubing comes in RED and BLUE??

There, I went and did it

-ERD50

 

[MRG]

+1, with all due respect!

Are you using pipe dope? Is it dope or tape specifically approved for gas?

A thread about dope?