(64) Rotary Stamp Mills in USA

I have been working with stamp mills for over 25 years and it has been  about 13 years since I have found an unusual "rotary" stamp mill. This was a smaller stamp mill and was designed to be moved around and used as a “Test” machine to check claims for gold values. The unusual thing about these mills is they are circular in design, not straight line as in the standard stamp mills

Design Presently, I have found only one manufacturer of these portable mills which was Straub Manufacturing Company that was located in Oakland CA. They started about 1909 from the information that I could find. The manufacturer points out many advantages to the rotary stamp mill. The mills are pretty much self-contained and does not take a lot of work to assemble them once on a proposed mining site. It eliminates the need for timbers, belt tighteners, and latch fingers to add to the complexity of the mill. With the inline mills it requires one vertical cam per stamp and with the rotary there is only one horizontal cam reducing the weight and added parts. The mill has cram springs that increases the force of the downward motion of the stamps. Most of the in-line mills just rely on gravity for crushing force. This design does away with banking of the ore that happens in the in-line mills with the ore being fed to the machine through a central port using an advance type Challenger feeder.

Specifications The following table shows the number of stamps, production capacity, power requirements total weight and heaviest piece.

Size	# Stamps	Capacity     24 Hours	Power Requirements	Total     Weight	Heaviest Piece
1	5	8 -12 ton	5	3953	450
2	10	12-15 ton	7	4785	650
3	14	20-30 ton	10	8000	1500

Mill Differences There were some small differences in the component orientation. They used both horizontal and vertical drive pulleys depending on where the drive motor was positioned. Not all mills had cram springs to give the stamps more power. Some mills had additional weights on top of the stamps to provide the added force. 

Advertisements The following are some early advertisements touting the ability of the rotary design stamp mill.

Existing Rotary Stamp Mills I was surprised to see the number of mills still in existence. I could find no quantity of these mills that were produced. I also could not find any other manufacturers that produced this special mill. The (6) mills below, one operational and five not working.