having problem with threading on radiator

JohnG

I needed to replace an old Maid O' Mist steam valve that was hissing steam from the rear (it was taking the paint of the wall in the bathroom).
Got it off ok but now can't get a new 1/8 angle steam valve into that same radiator (the kind that is slim design up into the wall).
The thread on the radiator seems to be bad. I've tried a few valves with no luck.
Any answers?
Thanks.

Andy Morgan_2

Try

running a pipe tap into the radiator. There may be some corrosion or other buildup in the threads. Be very careful, as the cast is brittle and you could crack the radiator! Not Good!

Good Luck


Andy Morgan

R. Morgan Mechanical, LLC

JohnG

thanks,

i picked up a pipe tap from Home Depot today but alas it is too small for the hole. I'll have to go back tommorow and get a bit bigger size.

It's fustrating that a simple job like replacing a valve can be such a pain on the neck.

The good news is it will warm up here in NY for the next 2 days to 40'....a little reprieve.

tim smith_2

thread hole too big?

You probably will need to drill it out and use a 1/4" pipe tap and then use a 1/4 x 1/8 brass bushing to bush down for the vent. Make sure the 1st tap you got was 1/8" npt.

JohnG

the tap and drill bit I bought was a Hanson 1/4-28NF #3.

It is too small for the hole. The plumbing person at HD recommended that I hand tighten it using an adjustable wrench. I would be afraid to take a drill to the radiator.

Kevinj

taps

I am not sure of the pipe size for your vent.......but a 1/4-28 NF IS NOT a pipe thread. It is a machine thread. 1/8" pipe is about 1/4" outside so as stated above, you need a PIPE tap, probably 1/8"

Wayne_12

1/4\" machine thread not the same as 1/4 taper pipe thread.

> the tap and drill bit I bought was a Hanson

> 1/4-28NF #3.

>

> It is too small for the hole. The

> plumbing person at HD recommended that I hand

> tighten it using an adjustable wrench. I would be

> afraid to take a drill to the radiator.

Wayne_12

1/4\" machine thread not the same as 1/4 taper pipe thread.

Bring the steam valve fitting along to match the size. What the sales person sold you is a 1/4 in straight thread with 28 threads per inch, or 1/4" fine thread.

I do not know if the steam valve is 1/8" or 1/4" in size. Bring the new valve in to match the thread. If the old one treaded out okay, then just run the tap into the casting to clean the treads, when the tap becomes hard to turn, quit and remove tap. Install steam valve.

It would be nice if all sales people were as knowable as possible. I find the local hardware stores more knowble about their products and will greet you by name.

WD

tim smith_2

type of thread

make sure it says NPT after the size, that stands for national pipe thread

JohnG

thanks!!

thanks for all the info. I'll go to a plumbing supply store tommw and get the right pipe tap.

cheers!
JohnG

masterplumb

I thought

it was nominal pipe thread.

tim smith_2

I'm pretty sure

its national pipe thread.

masterplumb

?

We sometimes see the abbreviation nom. which stands for nominal. I always thought it was nominal.I could be wrong. Chris

JohnG

problem solved

Thanks to everyone who assisted me on the valve problem.

I ended up getting the 1/8-27 NPT Hanson pipe tap and a new Heat-Timer Adjustable Varivalve ($19) from a local plumbing supply store in Massapeuqa.

The new valve still wouldn't seat so I used the pipe tap and then the valve went on nice and snuggly with some teflon tape.

**this is a great site**

thanks again!
JohnG
Massapequa Park NY

scrook_2

1/8 NPT pipe tap

You have the wrong tap! That's a tap for a 1/4" fine thread bolt.

You need 1/8"-27 NPT *pipe* tap (look for NPT!) It'll actually be about 3/8" in diameter at the threaded part, and it will be slightly tapered. A small adjustable wrench will work (you should able able to *start* the tap with your fingers), as will a tap wrench. You do not need to force it, just screw it in gently, as you are not tapping a plain hole but just cleaning up crud from the existing threads.

scrook_2

Actually it's:

[American] National [Standard] Pipe Taper

The applicable standard (if anyone cares!) is: ANSI B1.20.3-1976, R1991, but you can get all the dimensional info from "Machinery's Handbook", found in EVERY machine shop and EVERY machinist's toolchest in North America.

Pipe diameters, threads/inch, tap drills, etc. you can find in Thomas J. Glover's book "Pocket Ref" for sale here: http://www.heatinghelp.com/shopcart/product.cfm?category=2-22 for only $15, a bargain to be sure.

tim smith_2

NPT

gosh I am soooooooooooo confused, wish I knew for sure. Thanks guy's. I really don't know for sure what it stands for. Tim

Jim_19

NPT defined

Definition of pipe thread acronyms
NPT National Pipe Thread
FPT Female Pipe Thread
MPT Male Pipe Thread
PTF SAE short tape pipe thread
NPTF American National taper pipe thread for dryseal pressure-tight joints
NPSM American National straight pipe thread for mechanical joints
NPSI American National straight intermediate pipe thread