Stripped threads--a rookie mistake!

bob young

got one in manhattan. if you can weld it and gauarantee you got the job. but then that means i lose 15 K . TOUGH DECISION

Toolfreak

Stripped threads--a rookie mistake!

First, I'm not a plumber so excuse my stupid questions:

My old house (circa 1939) has a 1-pipe steam system. I was in the process of removing an air vent on one of the cast-iron radiators and noticed that somebody had crossed the threads at some point. So I bought a tap and gently tried to re-form the threads in the hole. After doing this, I tried to install a new vent only to find that the connection is very loose and leaking (even with teflon tape and pipe dope). The hole is now apparently too big. I think where I went wrong is that I used a non-tapered tap (instead of one for NPT threads -- see I'm learning!)

So, what do I do now? I obviously can't make the hole smaller.

Toolfreak

Keith_11

Hey. . . you've got yourself in a nice little situation with this. . . Radiator air vents are almost always 1/8th inch diameter pipe thread. Go to a plumbing supply, and get a 1/4 inch pipe tap and THE EXACT DIAMETER DRILL BIT NECESSARY TO PROPERLY TAP IT, no smaller, no larger. They'll have the reference book there, make sure you look at it yourself to verify you're using the right size. By the appropriate (cheap) drill bit, and drill out the hole slowly while pouring water over the bit - no oil, or it'll contaminate the system. Take it slowly, go only as far as you need to catch a thread. Get a 1/4" x 1/8" black bushing to bush down to the steam vent. Should take about 35 minutes, total.

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bob_50

Or

get some epoxy. bob

J.C.A._3

If you never plan on changing the vent again...

Bob gave some sage advice. If you want to change it in the future, go with the proper drill and 1/4 tap followed up with a 1/4X1/8th bushing.

Just like the drilling portion, take your time with the tap. Cast iron isn't the easiest material to work with but it CAN be done.(gently!) Chris

bob young

lampwick

try wrapping the 1/8 " thread with lampwick & teflon. use a 1/8 " nipple & elbow and a straight air valve the wick will build up to compensate increased depth of damaged tapping.

Rodney Summers

Huh?

What is lampwick?

Toolfreak

Ryan_10

Or if you're feeling adventurous...

You could try welding it and tapping it back to 1/8" if you have a stick welder handy. I've welded cast iron before. It isn't fun, but it (sort of) works with a good cast iron rod. I've got one radiator tht actually appears to have had one element welded on substantially at some point.

bob young

finally someone did it

congradulations mr.ryan. you are the first man that ever lived to sucsessfully weld cast iron. i was always told it was impossible. you could be a famous billionaire for achieving this breakthrough ! bravo.

bob young

go to a plumbing supply lampwick [ quickwick spool not the ball ]costs a buck & could possibly save the day for you.

Toolfreak

bushing

Why a "black" bushing? I could only find a brass one at Home Depot.

Toolfreak

brucewo1b

bob in defence of Ryan I must say you can weld Cast Iron. I too was also taught that you could not weld Cast Iron but have been shown the error of my ways. Now if not done properly it might not be pretty but it can be done.

Kevin O. Pulver

Bob, Bruce is correct

I was taught as you two were that welding cast is some sort of black art- impossible for all but magicians.
I have learned better. It's like soldering. Nothing to it when you know how. When you don't know how, it sure is frustrating and appears to be impossible. Of course I don't think welding would be prescribed in this case.
Kevin
P.S. I found this helpful post about cast welding on an antique engine board, enginads.com It's very interesting on cast welding. www.locknstitch.com/castwelding.htm

Ryan_9

We broke a cast differential...

casing on dump truck during one of my more fun summar jobs. Welded the crack up right on the truck and its still going. Before that, I always thought you couldn't weld the stuff too..

But hey, in this case, why fix something with a ball peen hammer when you COULD smash it back into place with a 20lb sledge. The sledge is much more fun. Welding rod, electricity, face masks... Really impresses the rest of the family.

bob young

brazing iron

you cannot weld cast iron. you can braze it but how strong it will be remains to be seen. it will be an unreliable patch. true welding is permanent once cast iron cracks that is it. fact.

adayton_2

Cast welding web link

is incorect. Correct loink is:

"" http://www.locknstitch.com/CastIronWelding.htm ""

alfred

Al Corelli

Lampwick can be your BEST friend.

Keith_13

Brass is more expensive but it's fine to use on steam.

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Kevin O. Pulver

Man will never fly Bob,

Never go to the moon, never overcome his obstacles, never achieve his dreams, never break the 4 minute mile, and never weld cast iron. Really? All you have to do is find the right guy and the right process. Just because you or I can't successfully do a heart/lung transplant doesn't mean it can't be done. Just because we've always been told it's impossible, and we've never seen it done, so what? Please look at the link and be pleasantly surprised. I was. Kevin