Since shoes have been installed on stamp mills there has been problems with shoes falling off their boss when operation is suspended for over several days. The problem is that the wood shims that hold the shoe on the boss dry out and the shrinkage causes the shoes to fall. When mills were put into operation initially they ran the mill basically 24/6. They ran the mill continuously for 6 days and then shut down on the 7th to clean the mill. They would bring the mill right back once the tables were cleaned off, that time being not much more than a day. During this time the wood shims did not get a chance to dry out, so the shoes generally stayed on the boss until the next run.
Today most of the stamp mills that operate only run for a short period of time and then shut down for several days or weeks on end. This gives the wood a chance to dry out and just when you are ready to run the mill you will see some of the shoes laying in the bottom of the mortar box.
There is really no solution other than running the mill all the time with short stops for maintenance or table cleaning. There are a couple of things that we have found to help keep the shoes on the boss.
One is to flood the mortar box overnight and let the wood swell up and hold the shoe tight on the boss. This has been recommended in the early stamp mill books. The problem is that it is hard to flood the boxes above the shoe to wet the shims. Mortar boxes are not designed to do that naturally. You have to dam up the outlet and flood it that way. It is a pain to take out the screen and place a dam in the outlet.
We found one thing that may help keep the shoe on the boss. We use a sock made from denim that fits over the wood shims, like a sock. This does two things. It holds the shims in place until the boss can be dropped on and also the denim holds the water for a period of time longer and keeps the shims damp and swelled on the boss. We have had some success with this operation. The picture below shows the production of socks being made on a sewing machine.
The picture below shows the shoe with the shims under the sock. The superimposed picture shows what the wood shim configuration looks like.
The picture to the left below shows the boss suspended over the shoe with the shims under the sock and ready to drop the boss onto the shoe. The picture on the right shows the boss dropped on the shoe and locked in place. You need at least a 1/8” clearance between the shoe and the bottom of the boss. You want to maintain at least 1/8” between the two components. You will notice the second shoe has about ½” clearance. You do not want much more than ½” clearance.