The Finished Part: Cartridge Brass

Dirty Cartridge Brass

Cleaning cartridge brass (see 'dirty' brass above) has traditionally been accomplished using a vibratory or barrel tumbler with a dry media such as Walnut Shell Grit or Corn Cob Grit. Both of these medias will do a good job of cleaning the dirt and oxidation off the brass but typically require a long cycle time (12-24 hours or more).

Alternatives to this long tumbling time are available that will result in clean, bright brass is as short a time frame as 10-15 minutes. These alternatives also require a vibratory or barrel tumbling system but with different media and use a wet (chemical compound solution) process. This post and the next will review the results using different tumbling methods as well as comparisons of different media.

The basic process involves (vibe or barrel) tumbling the brass with a polishing media. A typical ratio is about 3 parts of media to 1 part of brass by volume. The solution would be added to the level of the load in a barrel tumbler. In a vibratory tumbler, the solution could be circulated through the media/parts load or could be added as a small amount (usually about 5% by volume of the load size) in a batch process. The selection of compound (i.e, Kramco 1030 Mild Acid Cleaner) is critical to achieving good results. Obviously, it is important to ensure that the equipment being used is designed for a wet process.

Vibratory vs Barrel Tumbler

This picture shows the results using the exact same media type, parts/media ratio and solution but with different tumbling system types. The parts on the left were vibratory tumbled for 15 minutes with a recirculating solution of Kramco 1030 compound. The brass on the right were barrel tumbled also for 15 minutes with the same solution filled to the level of the load.

It is clear that both tumbling processes did an excellent job of cleaning the brass and that the results are very similar. Based on this test, it seems that either a barrel tumbling system or a vibratory tumbling system can be used to clean cartridge brass. The decision comes down to the type of equipment available and the desired in-house handling process.

The next post will compare different types of media all in a barrel tumbling process.