I found some very interesting information in “Drills and Mills”, second edition, book by Will Meyerriecks. There was information from the Homestake Mine stamp mill components life expectancy. It listed all of the major wear components in stamp mills in Leads, South Dakota. The information was taken from files that were kept on the mine site.
The table below shows the major components, material they were made from, weight and life in months. I was amazed to see that the stems were only good for about 4 months, only two other items have a shorter life and they are the dies and shoes. You would expect them to have the shortest life expectancy.
If you add up the weights for the tappet, stem, boss and shoe you come to 898 pounds. They were smaller than the standard stamp of 1,000 pounds. The boss on a 1,000 pound stamp mill would weigh more to make up for the weight difference. Most of the mills have a standard stem of approximately 14' long and 3 1/8" to 3 1/4" diameter. I'm sure that there were many odd-balls. The picture below shows that stamp mill at the Homestake mill.