Soldering metal - lamp shade repair

O.K. - should have looked more closely on line instead of accepting that

Plenty of 100W soldering irons for not much money, but 120W gets a tad expensive.

So I think I should rephrase the question into "how much power am I likely to need to spot heat this kind of structure".

I assume that I have to get the heat in locally very quickly so it doesn't just dissipate into the rest of the metal.

Cheers

Dave R

David laid this down on his screen :

A true 100w should manage it, but don't expect one of those instant trigger type 100w irons to cope. Like a gun, with a trigger and and a copper loop type element.

Whether soldering might be enough, is a different story. I suspect originally it will have been spot welded. You might be better looking up how to try that, with a 12v car battery.

If it is plastic, you will have problems with that melting. I thought these things were sometimes some sort of shell.

Given that the repair shouldn't be particularly visible, I'd be inclined to use a blob of epoxy.

The portholes are almost certainly flakes of windowpane oyster, aka capiz,

NT

Notwithstanding the issue about melting or damaging the inserts, I think you'd probably OK to solder the rings with a 45W iron. Maybe a little on the low side, but should be OK.

What's you're missing is flux. The surface is probably dirty, maybe painted. You need to get back to clean metal so that solder flows on the surface. You don't melt solder on the iron, you heat the metal and feed metal onto the surface. The only purpose of solder on the bit of the iron is to ensure good heat conductivity from the bit to the workpiece.

Likewise with a gas torch, you don't wave the solder into the flame, you heat up the metal and pool molten solder on the surface. However, I think a gas torch is way overpowered here and difficult to control.

Flux is the key to getting solder to stick to metal, particularly oxidised metal. You can use plumber's flux, but liquid flux is less viscous and easier to apply thinly:

The symptom of not-enough-heat is when solder on the bit solidifies when you touch the workpiece, and stays solidified no matter how long you hold it, or if you can melt solder on the workpiece close to the bit but not further away. If you can melt solder on the bit but not on the workpiece, you have a heat conductivity problem. If it doesn't stick, you have a flux problem. (or have non-solderable metals)

Theo

Also use tin/lead (60/40) solder rather than lead free solder. The former requires a temperature of around 190C whereas the latter typically 220C.

It may be beneficial to have a mechanical join before soldering. A turn of thin fuse wire or one strand from a multi-strand wire flex.

Even better, if you can get it, 63/37 tin/lead solder. Lower melting point, and the liquid to solid transition is fast.

You could use a combination of then both. The gas flame to heat it just enough so the iron can cope.

It's less power, than a very large bit, that wont cool down immediately it hits that ring

What metal is it? Soldering is quite a complex thing, as soldering dissimilar metals often needs special flux and sometimes different solder as well.

Brian

Or even wire the two bits together using solder, assuming its not too visible and not needing to be mega strong. Brian

Pretty much describes it - I can melt solder next to the metal, but not by applying the iron directly to the metal.

Which is why I tentatively concluded that it is a "lack of heat" issue.

On the back burner at the moment because I realised I have an identical shade in my bedroom so this is now a replacement in the living room.

Set of matching shades in the living room so replacement would have been tricky as The Range isn't showing them for sale at the moment.

Cheers

Dave R

I know it isn't spot welded because I melted the original solder - solder flows and sets in quite a distinctive way, as well.

For those commenting on the circles and solder, please note that I am taking about the ring that fits on the pendant light socket with a screw on plastic ring to hold it in place. So no soldering anywhere near other materials, thankfully.

Cheers

Dave R

In which case, I'd say more than 45W is required. The gas torch might do it, but it'll be pretty tricky to control.

I bought one of these while they were 9.99:

I didn't use it for soldering, but the element is like a red hot poker so I think it would do the job. It has quite a high thermal mass so the tip isn't likely to cool much when you touch something cold.

Theo

Ah, then forget solder, it's a very weak material.

NT