Vince Pitelka on tue 4 feb 97
Jonathan is right about using the correct machine for each job. Don't try
to mix clay in a pugmill, because it will be frustrating and time-consuming.
But if you can only buy one machine, consider buying your clay pre-mixed,
and get a pugmill to wedge your clay and reclaim scrap and save your wrists.
Figure out what your time is worth, and include that consideration when
choosing the right machine for your needs. Don't cut corners on initial
investment if it is going to mean lots of unnecessary labor in the long run.
Regarding the problem of bearings going out on pugmills and mixers, there is
often a very easy fix. Many mixers and pugmills have flange bearings
mounted directly on the end wall(s) of the machine, so that any clay which
is forced out around the shaft goes directly into the bearing. This is an
incredibly crummy design, and seems to me like planned obsolescence. These
bearings come with seals, but a seal fails quick in contact with clay
materials. In many cases, it is possible to re-install the bearings (or
when replacing the bearings) with spacers between the bearing and the wall
of the machine, so that there is a space of about 1/2". The spacers should
be steel. A one-inch square of half-inch steel plate, with a 1/2" hole
through the center (or whatever size is appropriate for the bolts in your
machine) is appropriate. For the very best set-up, this spacer should be
welded to the surface of the mixer - that way the bearing is held as rigidly
as if it were bolted directly on the wall. But I have also seen people
simply use oversized nuts, which slip over the shaft of the bolt and provide
appropriate spacing. It is possible that you might have to use longer bolts
to accomodate the additional thickness of the spacer, but I have not had to
do so on several machines where we have used this modification. You get the
picture. The spacer holds the bearing out about 1/2" from the surface, so
that any clay which is pressed out through the mixer-wall around the shaft
does not go directly into the bearing. Some machines come set up like this.
An additional improvement involves fabricating a large washer which is a
tight fit over the shaft. When installing the bearings, place this washer
on the shaft between the bearing and the mixer-wall, in the space created by
the spacers. Any clay which pushes out of the mixer around the shaft will
push against this washer, and the washer in turn will push against the
rotating portion of the bearing. Since the washer will turn with the shaft
and the bearing, it does not tend to wear out, and almost all of the clay
which pushes out around the shaft will be forced out to the side, rather
than into the bearing. A properly lubricated bearing, protected from clay,
should last almost indefinitely. An inadequately lubricated bearing,
unprotected from the clay, will fail almost immediately.
Jonathan has mentioned the imporance of preventative maintenance. From my
former life as a mechanic I can attest to the great importance of proper
maintenance. The bearings on a mixer or pugmill should be greased
FREQUENTLY, depending on how often the machine is used. On a machine which
is used very lightly, greasing the bearings once a month may be enough, but
on one which is used heavily everyday, the bearings should be greased
weekly. Checking gear-box oil is also important, but if it is good oil, and
it is not leaking out, it will last for a VERY long time. A bearing which
is not adequately greased will fail QUICK.
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts
1560 Craft Center Drive, Smithville TN 37166
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