How tight should radiator tails be

[Albumen]

I'm about (or maybe not!) to fit a towel rail. Just to make sure I know what goes where I just tried screwing the tail into the bottom of the towel rail. It's extremely tight, and only goes in a few threads before I really think I ought to stop. And this is without and PTFE.

Is this normal?

To try to compare, I started to have a look at a radiator I just bought. The connections for that seem to have some sort of daft plug in them with a sort of internal 4 knobbed thing. What on earth do you use to get that out? I assume it's a blanking plug to make sure nothing get's in during manufacture/transport, but I'm blowed if I can work out how to remove it.

Cheers, Mike

 

[Albumen]

Ok, replying to my own second paragraph, the little plastic plugs came out of the rad with a half inch chisel (used as a screwdriver). The tail ends go into that a lot easier, and only start to feel tight when there's about 3 or 4 threads left to go in.

The towel rail is so much tighter. Am I suffering from poor manufacturing tolerances here (cheapish thing bought of internet)? Whichever connector I try it's very very tight, though the second time it get's a bit easier. It almost feel like it's cross threaded or something, though when I take it out I can tell it's not.

Thanks. Mike

 

[JohnD]

is there any rust on the threads?

 

[TicklyT]

How deep are the threaded holes? On some towel rails there's only about 3/8" of material to put a thread in. A 1/2" BSP thread is 14TPI, so if it runs in about 4 or 5 turns, then it has gone the full depth of the female thread. The threads are tapered, so they will tighten as you screw them in.

I usually use an old 1/2" chisel I keep for opening paint tins etc. as a screwdriver to get the plastic plugs out of new radiators

 

[Albumen]

No, but there is some paint. It's brand new. When I say I bought it off the internet, it's not a 2nd hand thing off ebay or anything. towelradiator.co.uk infact.

I just tried another couple of times. Out of the 8 or so threads on the end of the tails, it goes in by about 4 before it gets very tight. Perhaps if I use one of the wire pipe brushes I've bought to clean the internal thread up a bit too, yes?

It feels a little like if I keep trying it'll gradually clean up the inside of the thread, but I'm not sure if that's a good idea.

Looking at the tails I'm a little unsure how it actually makes a seal. What I mean is there's not actual 'shoulder' to seat up against the radiator itself.

When I finally get to do this how much pfte should I be using?

Cheers, Mike

 

[JohnD]

it is a tapered thread, as TicklyT says, so it doesn't have to tighten up to a shoulder. If it is a proper fit, when it's tight, it's sealed.

Ig you think the threads are smoothing off as you screw and unscrew them, wind it in and out until you think it is as good a fit as you can get. Use no lubricant when grinding then against each other.

PTFE tape is extremely thin. I use overlapping turns so there are at least two thicknesses everywhere. If the thread catches it may tear the tape off. Push it right into the threads by turning it against your thumb. there are also jointing sealants that you can use on a threaded joint but they are now considered old-fashioned.

 

[Albumen]

Sorry folks, I'm not waiting long enough for people to post replies.

Thanks very much TicklyT, that explains everything. Yes, there's 10mm of thread on the towel rail.

And tapered!! That really does explain everything.

So the question now is:

1. Is it a good idea to clean up the internal thread a bit (I expect it would be better without the paint!)?

2. How much PTFE to use?

3. How much force to use (if that isn't a bit of string length thereof type question)?

Many thanks.

 

[JohnD]

tightness: as a rule of thumb, using a regular-sized spanner, you should be able to tighten things with your wrist. If you have to use both arms and brace yourself against a wall, it's too tight (though you sometimes have to do that when unscrewing)

That's why big spanners are longer than small ones. If you ever use a torque wrench you will be surprised at how little effort all but the really big nuts need.

 

[Albumen]

Great. Thanks very much JohnD and TicklyT. I appreciate your advice.

Just one more question, the other end, the compression joint, PTFE or not PTFE (that is the question)?

Cheers, Mike

 

[JohnD]

you can put PTFE on top of the olive.

I don't know how to do that, except by trial fitting and tightening the nut moderately. that sets the olive in place on the pipe and you can then tape it.

you aren't supposed to tighten it so much that the olive crushes a groove into the pipe.

I am not a plumber