alan
starting to spend too much on rocks
Member since December 2013
Posts: 111
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Post by alan on Feb 23, 2015 10:16:41 GMT -5
I tried my hand at trying to roll some sheet from some 14k yellow scrap... It ended in a miserable failure... I started by melting a blob of the metal on a soldering block and flattened it out with another pre-heated piece of another soldering pad... The initial piece was about 4mm thick but was still slightly rounded on the edges. One end was also slightly thicker, so I hammered it out on an anvil to try to get the metal more or less even. I followed the hammering by annealing at 1200F for 10min and quenching. The metal was cracking before I could roll it down to 3.75mm.... Cracking started on the rounded edge and worked inwards... I re-melted partially in order to fuse the cracks and attempted to repeat the process.. For my second attempt, I annealed after thinning 0.2mm and after 3 cycles the cracks were appearing again... Any advice?
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Tom
fully equipped rock polisher
My dad Tom suddenly passed away yesterday, Just wanted his "rock" family to know.
Member since January 2013
Posts: 1,557
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Post by Tom on Feb 23, 2015 16:25:14 GMT -5
You might try to raise your annealing temp to 1400 degrees. I don't work gold just found the info the net.
Tom
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ol3m3
noticing nice landscape pebbles
Member since September 2006
Posts: 85
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Post by ol3m3 on Mar 3, 2015 19:23:38 GMT -5
where did your scrap come from? any dental gold in the mix? Dental gold does not work well for casting and working afterwords and is brittle.
OM
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craigcis
off to a rocking start
Member since February 2015
Posts: 14
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Post by craigcis on Mar 12, 2015 23:13:51 GMT -5
I understand that there is an issue of saving money, but if you don't absolutely have to make sheet metal, DON'T. I have been a professional jeweler since 1976 and used to do this to save money, (Which I had darn little of when I was first starting out). The greatest advantage to it was that it made my arms stronger while cranking that #*%#$%^& mill. I learned early on that good clean metal was of the utmost in importance. If you have any solder in it, or if your metal has no fresh from the refiner grain in it, it will be brittle and begin cracking while rolling it out. Also remember that every time that you melt your gold in the open air, more oxygen fixes to the copper in your melt. Also, it helps greatly to use the most oxygen poor flame that you can get away with. Having that torch roaring away with an intense blue flame is not going to be a good thing. A really great method of getting a nice clean piece of flat gold to work with is to use two pieces of wood instead of a soldering block. Unless you are using treated charcoal as you block, you are probably using a neutral material such as a manufactured ceramic or magnesium pad that is chemically neutral. Wood will absorb oxides and is cheap to use. I take a piece of hard wood and a cheap end mill. Chucking the end mill into my drill press, I start the motor with the wood on the drilling platform and then crank the platform up until it bites into the board to just the depth that I think will be appropriate for what I am attempting. I then move the board around on the flat drilling surface. This makes a nice uniformly deep (flat) depression in the wood. The choice of how wide an area to mill out on this poor mans mill is up to you. I prefer to make the depression just slightly larger than what I expect the metal to cover in the end. The next step is to place your metal bits into the depression and melt it with your torch. Just as soon as it is molten, flatten it out by pressing down on the molten mass with the other block of wood. (Hard woods are best for this). The end result should be a nice shiny and flat billet with a little bit of wood grain pattern. Don't worry about the pattern. It will come out in the milling process. You are going to have some smoke and fire, so be sure to do it under a vent hood, or outside. The beauty of this method is that you will get a nice sweet and chemically clean billet of metal to roll out, without having to resort to expensive equipment. The second issue that you have is your annealing method. Heating it for ten minutes is just loading your metal up with oxides. The purpose of annealing is to return your metal to a state that is more conducive to cold working. When annealing gold or silver, I bring it up to the point where I can just barely see it beginning to give off a slight glow. Do this as quickly as possible, and then immediately remove your flame, thereby allowing only the most minimal amount of oxygen to combine with the copper in your gold or silver. Once this has been accomplished, cool the metal in accordance with the recommendations of your supplier. I say this, because each refiner will will have their own proprietary alloy that will either need to be quenched immediately, or allowed to sit. This is especially pertinent to the newer versions of silver and gold that have come onto the market. So you see, the basic rules are; 1. Never allow any metal that has, or is suspected of having scrap in it to get into your mix. 2. Use whatever reasonable and safe means possible, to keep oxygen away from your metal. This means quick melts and annealing heats with carbon rich flames (Don't over do it though. I didn't mean for you to use a sooty flame). Whew! My arthritic old fingers hurt!
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Tom
fully equipped rock polisher
My dad Tom suddenly passed away yesterday, Just wanted his "rock" family to know.
Member since January 2013
Posts: 1,557
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Post by Tom on Mar 12, 2015 23:27:11 GMT -5
That's facinating Craig. Enjoyed that read. Thanks
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gemfeller
Cave Dweller
Member since June 2011
Posts: 3,797
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Post by gemfeller on Mar 13, 2015 10:18:30 GMT -5
craig, that's excellent info from a real pro. I'm familiar with most of your points, as well as the use of charcoal for blocking. But charcoal blocks are expensive and your hardwood "fix" is very clever. Thanks for all the tips.
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craigcis
off to a rocking start
Member since February 2015
Posts: 14
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Post by craigcis on Mar 20, 2015 21:14:37 GMT -5
I'm just an old Marine who's proud to serve! Just don't ask me about rock tumbling. I have never done it. I have been giving it a lot of thought here of lately though. My idea has been to grind some stones to the general size and shape desired and then tumble them to completion. It just seems like it might be a more efficient way of getting the job done. But that's for another chat room, so I'll just leave it there for now.
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