To Cap It All

MichaelG:

You are quite right - apart from the screw thread, the cap in my photos above is certainly formed as opposed to turned and milled. I can't see any trace of solder, however.

The other cap I referred to looks like a brass casting and is much larger in overall diameter.

Jason, the originals had a thin top hat machined in brass which formed the thread and cap. The outside is knurled and a Bakelite cap bonded to the brass. I think Martyns best chance is to find a bit of brass and if lucky enough a big brass nut with enough meat to turn the internal thread, machine off the hexagon, crewcut the thread,silver solder a thick plate onto it, and machine the cap. Expensive exercise but it would be the joy of achievement. Chance of finding a 16tpi thread here in metric land would be like finding hens teeth - BUT good luck.

French Suppliers

Brass stop ends 2" BSP may be a possibility (2" BSP 2.347" OD) but the finished wall thickness may be very thin or non existent.

brass stop end

Or possibly something like this ??

Solder stop end

Bob

Ps, if Martyn would like to PM me, I have both cast cored bronze and some scrap marine bronze that would make the 1 1/2" diameter threaded portion here in France.

Bob

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Thanks for the confirmation

I had assumed [always risky] that the highlighted ring would have a solder joint

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MichaelG.

MichaelG:

You may yet be right about the solder.

I've tried to take a better photo having first cleaned part of the area you highlighted:

I recall learning from a recent post in another thread that solder comes in colours other than the usual silver-grey and if it is indeed soldered this may account for my not being able to distinguish solder from parent metal. I believe I took the possible joint line visible in the photo for the point where the boring tool stopped.

I take it that even a grossly-overheated radiator is not going to melt solder!

I haven't done the same with the outside surface as I didn't want to disturb the patina.

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Many thanks for taking the trouble to check … I’m intrigued by the production methods for items like this [not least because some of my ancestors were brass-workers].

Regarding the ‘grossly-overheated’ point : I did wonder if this might be a rather unsophisticated attempt at a safety valve !

MichaelG.

This is all wonderfully illuminating...and all to do with something very simple (ostensibly). I'm gratified that we all broadly agree an approach.

I find on the internet there's a company (in the US) called Sealcon that have thread adaptors that have a female PG29 thread at one end. That ought to get us half-way there. I haven't contacted them yet and there may be other suppliers closer to home.

If Bob so generously wants to provide a bit of marine bronze here in France I'm at

4 Place de l'Eglise, 80150 GUESCHART (it's on the Somme) I can pay in France no problem - UK, not so straightforward I'm afraid.

Thanks again for all the info.

Martyn

The radiator cap on my 1930 A7 special is a steel plumbing fitting of the correct thread with an old penny placed on the top which was then covered with plastic filler and carved to shape. Made some 60 years ago. Not by me I might add, but I approve!

Lee

Martyn, sent you a Private Message

Bob