3/4 equals .75

[Fletch78]

So why is copper pipe sold as 3/4 have an ID of .811 and OD of .875?


http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053

 

[TomSD]

Probably the same reason a 1x10 is actually something like 3/4 x 9 1/4... which is to say I have no idea.

 

[GilaMinumBeer]

http://en.wikipedia.org/wiki/Nominal_Pipe_Size

The reason for the discrepancy for NPS ⅛ to 12 inches is that these NPS values were originally set to give the same inside diameter (ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed and NPS became only indirectly related to ID and OD.
For a given NPS, the OD stays fixed and the wall thickness increases with schedule. For a given schedule, the OD increases with NPS while the wall thickness stays constant or increases. Using equations and rules in ASME B31.3 Process Piping, it can be shown that pressure rating decreases with increasing NPS and constant schedule.[4]

 

[Fletch78]

If it's a matter of nomenclature, .875 is 7/8ths, why not just sell it as 7/8th OD pipe?

 

[Fletch78]

http://en.wikipedia.org/wiki/Nominal_Pipe_Size

That is absolutely insane. "For tubing, the diameter is correct" so when you want to mate tubing with pipe, you are basically screwed.

 

[GilaMinumBeer]

Probably the same reason a 1x10 is actually something like 3/4 x 9 1/4... which is to say I have no idea.

This is also the Nominal dimension but the relevance is that the board is cut at 1x10 dimensions but after it is dried it is 3/4 x 9-1/4.

 

[david_42]

so when you want to mate tubing with pipe, you are basically screwed.

No, you merely have to use the correct adapter.

Boards - way back, a 2x4 was rough-cut to that size, then the board was dried and knifed down to the final size. That gave you a smooth board. Today, boards are cut to finished sizes using thin bandsaws. So, the lumber industry gets a bonus in every board.

 

[Fletch78]

No, you merely have to use the correct adapter.

Exactly. That's what I meant by "screwed". You have to buy 1, 2, 3, 8 more things.

 

[Bensiff]

I figure it is a vast conspiracy to keep homebrewers standing in the aisle of Home Depot for hours on end attempting to figure out how to make their clever new contraption fit together.

 

[TomSD]

I figure it is a vast conspiracy to keep homebrewers standing in the aisle of Home Depot for hours on end attempting to figure out how to make their clever new contraption fit together.

Haha that is why I'm always in there with a bag full of misc parts and a measuring tape. I just go around and see what fits that gizmo that I want to attach to that other gizmo. It is funny how many different places I find stuff too. I don't care what it was originally intended to be used for as long as it fits what I need.