Friday, August 7, 2015

Stamp Mill Guide Types

The purpose of this article is to show the various types of stamp mill guides that exist. There are generally two cross members with guides mounted, one near the top of the mill above the camshaft and the other below the camshaft. The purpose of stamp mill guides is to keep the stamps perfectly vertical during operations. This is a critical point since if the stamp were to become slightly out of a vertical position you could end up with broken stems and this could lead to other damage on the stamp mill. If one of the stems was to break and become lodged elsewhere it could cause damage to the other stamps and also damage the camshaft/bull wheel mechanism.  This could lead to catastrophic failure of the entire stamp mill. The life expectancy of a stamp mill stem is about four months and as you can see below it is one of the shortest life expectancies on the stamp mill, aside from the consumable shoes and dies that you would expect to wear out. Of course, if you exhibited good care the stems could last much longer.

Wooden cross members and wooden guides

In the early days of stamp milling the most common design was the two piece “sandwich” guides that would capture all five guides on a battery. They were made from (2) 4” X 12” X 57” rough cut timbers sandwiched together and then drilled with a 3 ½” forcner bit. The picture below shows a typical wood guide construction.

Another early design is similar in the material used, but each stamp had its own guide and this was a little more work to fabricate, but gave some flexibility for repair work. You could work on one stamp at a time. With the previous design you would have to take the entire 5-stamp battery out of service to access one stamp. Individual guides as shown below gave the millman some flexibility of repair during operations.

Wooden cross members and steel guides

There are stamp mills that have wooden cross members and steel guides installed on the wooden cross members. This is very similar to the individual wood guides that were mounted on the wooden cross members. It allows individual removal of stamps keeping the other intact during operations. The stamp mill below has steel guides that were fabricated by the volunteer team. Another advantage of the individual guides is that they are adjustable and can be moved slightly to allow better alignment between the stamps.

The next guide is a manufactured steel guide that mounts on the wooden cross members. This too has the ability to remove one stamp at a time and is a simpler device than the one above.

The guides below are still steel on wood, but the guides are made from a single steel plate that has 5 stationary brackets that hold the guides together. You can still remove only one stamp if necessary, but cannot make individual adjustments.

Steel cross members and steel guides

There are also steel guides that have several different constructions. It seems that Australia and New Zealand have a large number of steel constructed guides. I spent some time in Australia and New Zealand and visited many stamp mills. The picture below shows a stamp mill with steel guides and wooden uprights. They are similar to the first wood guides in this article, made from a two piece construction sandwiched together. This will not allow individual removal of stamps or any individual adjustment.

The stamp mill below is completely made from steel with steel uprights, cross members and guides. This will also not allow individual stamp removals or adjustments.

The stamp mill below is another mill completely made from steel. Part of the reason why steel was used in weather that is semi-tropical where ore crushing was done was to prevent battery deterioration. The mill uprights below was an early model since it has square bosses that accept a square coned shoe. 

There may be more different styles of guides, but this is what I have observed in my travels. The guides are an important component of the stamp mill mechanism and deserves recognition.

The End

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