Thread engagement

[Dexter]

Hi all, new to the forum. I need to install a bunch of steel reducing hex bushings into 1" cast fittings and was curious on how far the pro's crank them in. I realize bushings are frowned upon and often unacceptable, but I am clear to use them in this instance. A co-worker told me they must by tightened until all the threads are buried and the face touches the fitting it goes into. Seems off to me, but is he right? If so, is there documentation to back it up? Thanks in advance for your inputs

 

[frodo]

what are te cast fittings going to be used for ?

 

[SHEPLMBR]

Hi all, new to the forum. I need to install a bunch of steel reducing hex bushings into 1" cast fittings and was curious on how far the pro's crank them in. I realize bushings are frowned upon and often unacceptable, but I am clear to use them in this instance. A co-worker told me they must by tightened until all the threads are buried and the face touches the fitting it goes into. Seems off to me, but is he right? If so, is there documentation to back it up? Thanks in advance for your inputs

They would not pass code here if it is for gas.

 

[Dexter]

It is for a sprinkler system

 

[frodo]

if you bury the thraeds you will bust the fitting


npt sch 40

14 threads on a 1/2 and 3/4 pipe

and they should be effective tight with around 7 or 8 threads inside a fitting

depending on pressure of system.

 

[Dexter]

Well these are 1" npt, and research Ive done tells me that maximum engagement should be 6.5 threads max. I've seen plenty of fittings get busted from over tightening, as you say. I've tried explaining this, and asked what literature he saw that stated bushings need to be bottomed out, and he told me to 'look it up'. I've tried to find it and cannot! lol