shaping 18ct yellow tubing

**ajda** · 16-12-2015, 11:29 AM

I want to shape a piece of 18ct yellow gold tubing (4mm OD, 0.5mm wall) in a similar way to this piece of silver. With the silver it's easy enough to do by pinching with round nosed pliers, going gradually and annealing carefully. I've only worked a little in 18ct gold - any advice for doing it neatly and avoiding splitting?

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Alan

**Dennis** · 16-12-2015, 02:23 PM

An unusual request Alan and having previously done it with silver, you are already the expert on this. However 18ct will be harder than silver, even when annealed.

If I were doing this without prior knowledge, I would have one more go with silver or cheaper tubing from a model shop. I would start it with pliers, possibly large handymans wire cutters. Then I would see whether I could improve it by laying it flat, inserting a blunt table knife and rolling it. No idea whether this would give a better result, but experimentation is part of the process. Dennis.

**ajda** · 16-12-2015, 08:26 PM

Thanks Dennis. I thought the main difference would be hardness - I recently read a comment from a goldsmith who described working with silver as like working with butter. I've had several goes at this with the silver tubing - actually doing the same shaping operation as I plan for the gold, but for a quite different purpose (sounding enigmatic, I know, but I'll post pics/details of both further down the line), at the same time using the silver as a test run for the gold. I've been studying Cookson's datasheet on 18ct yellow gold and making comparisons with what I know - so, for example:

Annealed Hardness 120 +/- 10 HV
10% reduction of area 150 +/- 10 HV
20% reduction of area 180 +/- 10 HV
40% reduction of area 215 +/- 10 HV

Argentium, by comparison is around 50-60 annealed and up to about 120-150 fully hard.

It also says "May be cold worked up to 70% thickness reduction between anneals" - for Argentium up to 60% reduction is recommended.

So, I've got some theoretical understanding and some experience with silver to relate it to... but I guess I'll need to play with a lot more before I really get a feel for it. I just hoped someone might look at my picture and say, hey presto, here's a simple foolproof method for doing that. I suppose I'm nervous about getting started - £300 worth of gold just arrived in the post and there's not a lot there. I can't really afford to get it wrong, whereas with the silver it doesn't matter - I just melt down any botched attempts and make something else with them.

Ah well, I shall grit my teeth in the morning, take up torch and pliers and see what comes...

Alan

**ps_bond** · 16-12-2015, 08:35 PM

I'd be inclined to fill the tubing, either with pitch or Woods metal. Could then use a punch & pitchbowl (or sandbag) and chase in the groove, or get carried away and make a small smithing magician (AKA a butcher).

Or go with the pliers.

**ajda** · 16-12-2015, 10:13 PM

I'd been wondering about filling the tube to give it some support on the inside - probably a sound idea, though I didn't know what to use. So, different types of pitch... Wood's Metal... I've not worked with either... what would you recommend for a novice?

Smithing magician/butcher... that's a new one to me - I've just been asking Google about it - I might not try making something specific for this task but I can see lots of future possibilities there... Right now if you could lend me a magician of the Harry Potter kind that would be great.

I've left myself one week (busy already) to do something pretty complex that I've not done before in materials I'm not very familiar with. Deadline pressure works well for me, so that may be no bad thing. It's for a family member, so there's room for forgiveness (I hope) if it all goes pear-shaped, but obviously I'd like to get it right.

I will post pics here when it's done, even if it's a pear...

Alan

**ps_bond** · 16-12-2015, 10:22 PM

Pitch probably has more additional uses than Woods metal; you could either use traditional asphaltum pitch (um, or roofing pitch in a pinch) or a soft pine rosin-based pitch (often "German Red Pitch"). David Huang uses microcrystalline wax when chasing vessels, including his pure gold one; I've started trying that for some of mine - candle wax might work, but I suspect it'll fracture more. Worth trying to see though, work with what you have. I'd be leary of trying low temp solder, even if it is lead-free. You might get away with it if you soot the inside of the tube; it shouldn't wet gold, but sod's law takes precedence.

Funnily enough, Jim Binnion & Chris Ploof have started marketing something similar for drawing down mokume billets in a hydraulic press. I'd probably just make one up from scrap though.
http://www.riogrande.com/Product/pre...c-press/115907

Added - video:
https://www.youtube.com/watch?v=2de_qgmTUAg

**Dennis** · 17-12-2015, 04:03 AM

I have wracked my mind from the beginning as to how one could support the inside. It would be quite challenging to fill 4.00mm tubing with a liquified substance and be sure it was completely full. Also messy to remove.
Tonight I found some electrical lead, where the plastic covered strands fit tightly into this size of tubing. By slightly bevelling the opening with a round burr and using a little lubricant, it can just about be screwed in.
If this improves the result, then by leaving some protruding at each end, it can eventually be removed by holding the tubing back against the front side of a drawplate, or hole in a piece of stiff metal such as brass and pulling with pliers-possibly the wire first and then the plastic.

A completely different approach would be to use two stubs of tubing, make about 6 short cuts in the end of each, stand them into a fitting hole in a doming block or plate and gently dome them shut. You have to go slowly, or they buckle. Also hold them upright with tweezers, to save your fingers.
Then use solder to obscure the traces of cuts, lay them touching in a groove made in a block, reheat and they will join. Dennis.

**ps_bond** · 17-12-2015, 06:11 AM

Agreed, it's not going to be the easiest thing to fill. Copper wire dissolved out with nitric acid would be another solution (no pun intended), but not everyone has nitric.

**ajda** · 17-12-2015, 07:36 AM

Dennis, your electrical cable idea could be the one. I'd been thinking about various things I might find to use in garage/kitchen/junk drawer, but worried about getting anything stuck inside the squished tubing - the fact that you could draw out the inner wires and thereby free the plastic outer from its tight squeeze could be the answer...

I'm tempted to get some pitch anyway, as I know I have other uses for that - and since I've got order something else from Cookson, I might just get a lump from them. They don't give much detail on the site about the different ones - would I be right in assuming these two are similar, perhaps different hardness?
http://www.cooksongold.com/Jewellery...rcode-999-0099
http://www.cooksongold.com/Jewellery...rcode-999-0104

Your idea of doming the ends of shorter pieces then joining them probably won't be practical in this case - I need to make 3 parallel grooves in two short lengths - but I also need to dome the ends slightly as well, so you've given me some useful clues there.

I probably wouldn't consider the copper/nitric acid route - not least because I think you have to have an EPP (Explosives Precursors and Poisons) licence nowadays for that - but out of interest, would nitric not also attack the copper content of a gold alloy?

I'm still thinking about the magician. I've got a small arbour press lying idle in the garage...

Alan

**ps_bond** · 17-12-2015, 07:46 AM

Originally Posted by ajda

Dennis, your electrical cable idea could be the one. I'd been thinking about various things I might find to use in garage/kitchen/junk drawer, but worried about getting anything stuck inside the squished tubing - the fact that you could draw out the inner wires and thereby free the plastic outer from its tight squeeze could be the answer...

Reminds me of another trick - grab both ends and stretch the inner core, although I don't know if you'll get enough change in cross-sectional area to free it - it's probably that the necked-in section would fail first.

I'm tempted to get some pitch anyway, as I know I have other uses for that - and since I've got order something else from Cookson, I might just get a lump from them. They don't give much detail on the site about the different ones - would I be right in assuming these two are similar, perhaps different hardness?
http://www.cooksongold.com/Jewellery...rcode-999-0099
http://www.cooksongold.com/Jewellery...rcode-999-0104

Not familiar with either of those particular ones, sorry - but of the 2 I'd go for chaser's pitch first. Wondering about Polymorph, but it's quite firm.

I probably wouldn't consider the copper/nitric acid route - not least because I think you have to have an EPP (Explosives Precursors and Poisons) licence nowadays for that - but out of interest, would nitric not also attack the copper content of a gold alloy?

For a private individual, yes. Yes, it'll attack some of the copper on the surface but not to a significant degree.

I'm still thinking about the magician. I've got a small arbour press lying idle in the garage...

There're comprehensive plans around - LMK if you don't spot any, I'm bound to have some on file somewhere.