The following guide for steel shot burnishing provides some basic guidelines prior to using steel shot in either a vibratory tumbler or barrel tumbler.
Burnishing with Steel Shot in a Vibratory Finishing Machine
- Vibration setting should be set at a maximum or close to maximum.
- The tub or bowl should be filled 55-75% with steel shot and parts.
- Use a volume ratio of three parts steel shot to one part of parts.
- Use a mixture of large steel shot (3/16″ – 50-70%) and small steel shot (1/8″ – 30-50%). Large steel shot increases action.
- A small quantity of water should be pumped into the tub or bowl.
- A ratio of one ounce of liquid compound to each gallon of water is recommended.
- Compounds that contain soap (usually powders) should not be used. Instead, a liquid compound with a detergent component is advised.
- Steel shot will not burnish if it is not polished.
- Change compound and water every 4 hours of operating time.
Burnishing with Steel Shot in a Barrel Tumbler
- The most effective action in a barrel tumbler is achieved when the barrel tumbler is filled to 50% of its total capacity. At this level, you will also find that your parts are less likely to damage each other. With this in mind, fill the barrel halfway with steel shot and parts. Use a volume ratio of three parts steel shot to one part of parts (i.e. jewelry).
- Place sufficient water in the barrel tumbler to cover the load (shot and parts) by 1 to 2 inches.
- Add 1 teaspoon of Kramco 910 Burnishing Compound for each quart of water. The barrel should be rinsed out after every run. Fresh water and compound should be used for the next run.
- Processing time for burnishing can be from 1 to 20 hours. Soft metals will take less time than hard metals. When the object of burnishing is to brighten recessed areas or produce a smooth surface, the run will take a minimum of 3 to 4 hours.
- Store steel shot in a barrel or plastic container. Cover steel shot with water and a rust-inhibiting compound.
- Steel shot will only polish if it is bright and light colored.
Procedure for Cleaning Dark or Lightly Rusted Steel Shot
Rinse out barrel. Add sufficient fresh water to cover the shot by one or two inches. Add one teaspoon of Kramco 750 to the barrel for each gallon of water. Run for one or two hours. Repeat if shot is not bright and light colored. Rinse out after run. You can now begin normal burnishing process.