Sizing a platinum ring

by platinum on October 20, 2008

Q: How do I size a platinum ring one size smaller?

A: The essential features of a quality sizing are: a proper fit, invisible seam, and an even shank thickness. The following procedure will leave no seam and is totally invisible.
1. Cut the ring and remove 2.54 mm of shank. Bend the ring together until the ends meet.
2. Using a three square file, file a chamfer (v-groove) along the seam. This ensures a complete fill of the seam during welding.
3. Roll the piece just cut out from the ring through the rolling mill making it approximately .5 mm thick. Cut a small piece from this and wedge it into the gap with
the chamfer groove. It should stick out approximately 1 mm, evenly around the cross section of the shank.
4. Wearing #5 welding goggles, use an oxidizing flame of a propane/oxygen, hydrogen/oxygen or natural gas/oxygen mix and melt the over hanging metal all around the seam, filling the gap as it melts.
5. Quench or let cool, gently file away excess metal, and round the ring.
6. Clean and polish. Be sure there are no scratches, pits, or marks. Check size and make adjustments if necessary. Because the metal used to fill the gap was from the host ring, there will be no seam, therefore sizing is invisible.
Tips on what not to do:
Don’t use Acetylene Gas. Only Natural Gas, Hydrogen or Propane will work for Platinum
Don’t weld without eye protection. UV radiation WILL damage your eyes
Don’t weld when stones are nearby. The welding process will damage most stones
Don’t use your soldering pick or steel tweezers near the flame, as they may contaminate the platinum
Don’t weld on a charcoal block. Platinum and Carbon do not get along


Q: How do I size a platinum ring up?

1. Using a side cutter, cut the shank from the right and then the left. This will create two opposing pointed ends. Spread the shank open to the desired size using a mandrel. 
2. Cut a piece of sizing stock to the required length for the desired size. Using a saw, cut a V-shape on either side of a piece of sizing stock. File it to fit on the shank ends. Check for fit. 
3. Insert the piece of sizing stock into the ring. Be sure it fits snug. 
4. Using hard 950 platinum solder, solder the piece of sizing stock to the shank. Be sure solder flows all around. 
5. After filing the inside, round the ring on the mandrel. This will also work-harden the shank for easier finish. 
6. File, sand, and polish the ring after the dove tail sizing.

Pick sizing stock of the same alloy as the ring to assure color match.
Pick sizing stock of the approximate dimension of the actual ring. This will reduce filing and waste.
Be aware of stones in the ring. You may need to protect or remove them before sizing.
Make the ring about 1/4-1/2 sizes small and hammer the shank to the proper size. This will harden the shank and finishing will be easier.
Remove all scratches with fine abrasive paper before polishing.
Be sure and replace the quality mark (Pt950).




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