Wednesday, August 13, 2014

Stamp Mill Mortise & Tenon

There are two major locations where mortise & tenons are used in stamp mill construction. They are in the stamp mill feeders and the stamp mill uprights. The following are details on the use of the mortise & tenons.

Stamp Mill Feeders: The floor model stamp mill feeders are constructed of 4X4 timbers that are assembled with the use of mortise & tenons. It is a very stable and strong configuration to use. The feeders take a lot of rough punishment from the action of the stamps pressing down on the feeder actuators, and with about half a ton of material in the feeders it can be very hard on the framework of the feeders. That is why they use this type of configuration.
The restoration of the feeders on the American Boy 10-Stamp Mill (Goffs, CA) was completed by using the original timbers as patterns to make the new timbers. The pictures below show the before and after conditions for the feeders on the American Boy mill. The Golden Reef 10-Stamp Mill (Cave Creek, AZ) did not have any of the original timbers for the feeder, and we had to redesign the feeders so that they would properly fit the mill.  

The feeders needed to be disassembled and the wood parts saved and used as patterns for the new feeders.

The mortise and tenons make the feeders extremely strong and allow them to take a beating and keep working. The picture below shows the mortise & tenon wood cuts and also the method used to attach the mortise & tenons together.

The results are a very strong joint that will hold the several hundred pounds of ore and deliver it to the mortar box. The picture below shows two views of that assembled joint.

Once you have mastered the art of making the mortise, tenons and the bolting configuration you can go onto making the mortise, tenons and joints for the feeder and assembling the feeder.

The assembly stages are shown below: 

The finished product below yields two feeders for the American Boy 10-stamp mill.

Stamp Mill Uprights The stamp mill uprights generally have a mortise and tenon where they come in contact with the stamp mill base timbers. I had found two occasions to work with the mortise & tenon in the area of the bases. The first were uprights that were too short to be used as is on this stamp mill. It was a 10-stamper and the center timber was not only too short it also had rotted about 2 feet up on the upright. You can see the condition on the picture below:

The first thing we had to do was to make up a template of the tenon. The table below shows the dimensions that were taken off the original mortises. This is an important step since the mortises were not all the same size and orientation on the uprights.

The next thing was to purchase the pieces of lambeams for this particular mill to replace the rotted wood which included (2) 12” X24” X 22” and (1) 9” X 24” X 35”. Each mill replacement would be different. The center timber was thinner than the outside timbers. The timbers were ordered to size. All we had to do was drill out the mortise for each timber, using the patterns that we had made up.

Once the rough holes are cut out with the forcner bit the rest of the material is taken out with a chisel as shown below to “hand fit” the two pieces of wood:

The next step is to put glue on the pieces and clamp then in place and drill holes and install wood pins in the side of the timbers going through the upright where the tendon is located.

The final completed mortise & tenon installation on the American Boy 10-Stamp Mill.



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