Introduction
This open-ended necklace is to large to fit into a tumbler and must be hardened on the mandrel
When you shape metal, such as around a mandrel or in a form, it will start to become tougher. The metal doesn’t feel tougher because your starting to get tried from bending it, it is actually getting tougher because as the metal is formed by the hammer or by bending the bonds start to change at the molecular level making them tighter. In some cases, as in making your own sheet, if the bonds get too tight the metal will start to tear at the edges like a piece of paper. Luckily this can easily be fixed by annealing the metal.
Now there are times that it good to work harden metal on purpose. For example I make earrings out of 24-gauge silver, which is very thin. If I sold earring right after they have been annealed they could easily bend. Now if I work harden them they are tougher and can take more of a beating. There are two primary methods for work hardening metal, the first is with a hammer or the other is with the tumbler.
Hammering
The hammer has some major pros and cons when it comes to work hardening. The first major pro is that the hitting process really hardens it quickly. This is true whether your hammer it against a hammering block or a bracelet mandrel. The second advantage is that you can harden specific spots more then others, such as the back end of a wire necklace. The third advantage is that you can work harden pieces that can’t fit into a tumbler such as large necklaces or bracelets.
However, there are some disadvantages. First hammering is loud and if your studio is in a small apartment like mine noise is something you need to think about. Second work hardening is labor intensive, it could mean hitting the same piece over 20 times on a mandrel. The third disadvantage is if you mess up or if the mandrel is damaged, hammering can do damage to your piece by adding unwanted texture.
There are also times in which hammering is not an option. I will give you an example. When I make quarter dome earrings I dome the half circle slices which then work hardens the silver. But when I solder the jumps rings on for the earring hooks it anneals the metal and makes them soft again. Because of the big rings on the back side I can’t hammer the domes again. That is when the tumbler comes in.
Tumbler
with a difficult bezel setting it best to use the tumbler minimally
The tumbler is primarily thought as of a cleaning tool. It is an excellent cleaning tool and something all jewelers should buy early on. Another advantage of the tumbler is that while it cleans your pieces it also works hardens them. This is because as it sloshes around in the shot the rubbing process work hardens the silver, copper or gold that you have in there.
Now this seems like the best solutions because of two reasons. First, your going to use the tumbler to clean your pieces anyway so its two birds with one stone. Second, the tumbler requires minimal amount of labor, which allows you to make a higher profit on the piece.
There is a problem with the tumbler though is that it work hardens every part of the piece. That means if you have an area of the piece that you don’t want work harden, such as a bezel cup, the tumbler might not be your best choice. Trust me if you run a piece with a bezel cup in it in the tumbler for a few hours be ready to use some muscle to get that stone in. Usually with bezel cups with tough bezels, such as sharp corners, I will only run the piece in the tumbler for about an hour then hand polish.
Conclusion
Work hardening metal is part of working with metal. For complex forming annealing the piece several times can be necessary. It is also important to remember to work harden a piece before you put it out there to be sold. This is particularly true for fine silver, which is much softer then sterling silver and even after work hardening bends easily. Remember use the tumbler sparling for pieces with bezel cups because setting those stones with work hardened bezel can require some elbow grease.
