Resizing signet ring

Hi everyone -

I've been give a man's 18ct yellow signet ring to re-size. I've done many before, always by tapping on a mandrel, as they've only needed to go up 2 sizes or less. But this one has to go from size M to Q. The shank is 4mm at the widest down to 3.6mm where it's worn. D-shaped with a high profile and 1.7mm thick. So there's plenty of metal, but can this be made so much bigger by tapping?

I know I could add gold, but a couple of things concern me. The face is engraved (though not seal engraved) and I wondered if heat - even annealing - might soften the crispness of the engraving? Is there any way to protect it? Also, there is a faint shadow line from the original solder and annoyingly, it's about 1.5mm away from the hallmark. I can be precise and mask the hallmark, but can I solder that close to it without damage?

I'd be grateful for your thoughts please!

I think that if you don't anneal, you will risk cracking the shank as you go on expanding, so annealing by heating is inevitable whether you decide to expand, or to add a piece.

You can protect the engraving against direct flame with a splodge of Technoflux and cover the hallmark to repel solder by brushing on a thin paste of powdered rouge in meths and letting it dry.

The only problem will be not to wet the rouge with your flux, or it will run into the joint.

The customer should be warned of your concerns and then decide whether to go ahead. Dennis.

Good advice - gratefully received!