Shoe
& Die Needs Both of these items are a very
important piece of the stamp mill and without them the mill ceases to operate.
Miners were constantly adjusting and changing shoes and dies out on the mill.
Depending on how hard the host rock is determines how often you have to adjust or
change both components. Remember, they had to maintain a specific crush height.
The shoes and dies had anywhere from 6" to 9" of wear material.
The
(10) new shoes below have about 8” of good wear material and the dies have
about 6" of wear material. Remember, also that the shoes wore down faster
than the dies. That is the reason for the difference in wear material quantity.
The picture below was taken in Ballarat at the Sovereign Hill 10-Stamp Mill in
south eastern Australia.
Shoe
& Die Materials The
following information was used for operating stamp mills back in the day where
they were run 24/6 as production mills. It states in “Stamp Mill A Treatise on Practical Stamp Mill & Stamp Mill
Construction” under the Shoe Topic that Shoes are made of cast iron, forged
steel or chrome steel, the last being the best material.
Shoes wear down faster than dies,
therefore he suggested that you use shoes made from chromium and the dies made
of a good forged steel. This will give you a longer life expectancy and less
labor and time to change out the shoes.
All of the above information is for a “production”
mill. The mills that I have worked on are run only for 15 to 20 minutes for maybe
once and week to once a month or so. The wear will be negligible. I have been
running a 10-stamp mill for over (7) years on an average and there is
negligible wear on the shoes and dies. Depending on the cost of the materials
we could go with a “forged steel” material and would suit us fine.
Making
Casting Molds The shoes
and dies are cast from molds. The shoe and die molds are made from wood that
forms a sand casting around the mold, the mold removed and then metal poured
into the casting. There are a couple of factors that go into the making of
shoes and dies with their associated thicknesses and diameters. The following is
an explanation of some methods of how the molds are made:
NOTE: I would like to recognize Dale McBride
for all of his work on coming up with the multiple layer designs for the shoe and
die molds. He spent many hours perfecting the design and building the forms in
his shop. This project would not have come to reality without Dale’s knowledge and
expertise.
Shoe
& Die Thicknesses Back
in the day the millmen would adjust the tappets to maintain the correct crush
zone during operations. The first thing that needs to be said is we “do not”
like moving tappets. Most of the tappets have been rusted on the stamp stem for
many years and they are very hard to move, once you move them, they do not want
to stay in place, and finally there is a breakage possibility. Most of the restorations
I have worked on do not have dies and tappets of the correct size and when
there are, they are all different sizes that would require tappet adjustment. Sometimes
there are no shoes or dies and you have to start from scratch. To make things
easier we would like to be able to make different size shoes and dies to obtain
the proper crush zone. The shoes would have a minimum thickness and then you
could add pieces to the mold to make the desired size. This could be done for
both the shoes and dies and would only require one mold. The drawing below
shows the stacked ¾” removable pieces.
Shoes
Sizes We have dealt
with many sizes of shoes and dies with diameters 6”, 8”, 8 ½”, 9” and 9 ½”.
Most of the shoes were 8 ½” to 9 ½” in diameter. You can have a shoe little
over or undersized and get away with it. The cone diameters on the shoes are
different sizes, but you can always use different size wood shims to make up
for the diameter differences. I have placed a drawing of a shoe with the most
common dimensions. This will probably work for any of the standard 8” projects
that are presently in progress. The following considerations were taken for the
shoe molds:
Shoe
Removal from the Casting
The shoe needs to be tapered so that the casting will slide out of the sand mold.
The shoe will sit in the mold with the cone facing down. The taper of 1/8” over
the 6” should be plenty to allow removal of the form and later casting from the
sand mold.
Multiple
Shoe Sizes We have made
molds with (4) ¾” removable pieces to make multiple shoe sizes for various applications.
The pieces will be held on the mold with bolts sized for each thickness. This
will allow us to get the proper crush zone of 5” between the bottom of the shoe
and the top of the die without adjusting with the tappets.
The drawing below shows the shoe mold. I
think we have covered all aspects and have decided to go with forged steel in
the discussion above. It appears that the shrinkage of the steel should be a
factor, so we will take that into consideration later in the discussion.
Dies The dies are a little more restrictive
since some mortar box producers do not make a” standard” size. With the dies the
mortar boxes are pretty much a standard length of 57” on the outside, but the
inside width becomes an issue when you have smaller dimensions.
The
following considerations were taken for the die molds:
Die
Removal from the Casting
We have tapered the die so that the mold will slide out of the sand casting and
also slide out of the casting once poured. It seems the taper of 1/8” over the
6” is enough.
Multiple
Die Sizes We have made
a mold with (4) ¾” removable pieces to make multiple shoe sizes for various
applications. The pieces will be held on the mold with bolts sized for each
thickness.
Casting shrinkage I would like some help on how much larger I
need to make the mold is we used the forged steel material. The table below
shows the metal shrinkage %.
The drawing below shows
the die mold. I think we have covered all aspects. We have decided to go with
forged steel in the discussion above and need to know how much larger the
dimensions should be for the shoe and die.
DIE MOLD
The
pictures below show the finished die and shoe molds. The shoes and dies can be
made different thicknesses by removing or adding layers of wood. The cones can
also be removed and smaller or larger cones can be installed if needed.
This
process will be used at the Gold King Mine in Jerome, AZ since they need
different sizes shoes and also the cones are different. We can make a different
shoe cone for all 5 shoes that have different boss dimensions. I have never
seen a mill with the extreme differences as the Gold King Mill.
Gold
King Boss Dimensions We
found that the bosses on the Gold King Mine dimensions were varied and we
needed to find out if one cone could be fabricated to fit the cones into the
boss. Dale made up a cone that used the smallest cone dimension of the five
bosses and sent it to me with several different shims to see what size cone/s
would work.
The pictures
below show how we will figure the angle inside the boss. The device will be
placed across the bottom of the boss and the angle measured. The angle on the
cone is about 83°. This device will be used to make sure that we get the angle correct
on the bosses at Gold King.
The
pictures below show the “test” cone with top of the cone being 3 ¼”, the bottom
of the cone being 4 3/8” and the height being 5”. This cone matches the
smallest boss diameter at Gold King. We will install shims to verify each of
the boss dimensions using the shims to verify if this cone can be used for all
5 stamps.
The
final step in this project is to communicate with foundries that will still
cast shoes and dies. We are considering two Foundries that could do the job. I’m
estimating the cost should be between $2 and $3 per pound for cast steel, coming
to about $150 each
Kit’s
Foundry & Machine Inc Anaconda
Foundry Fabrication Company AFFCO
779 E.
1100 N 1015
East Sixth Street
Shelley,
ID 83274-5222 Anaconda,
MT 59711
To
give you an idea of the cost of a shoe and die back in the day, December 23,
1913, cost $21.00 each for a chrome shoe and a die. The
shoes we are looking at will be made from the cheaper cast steel.
THE END
