The Flat Lap
is part of a series on cold working equipment. Click here to
check out the beginning of the series.
The flat lap (sometimes called a flat bed grinder)
used for grinding a flat surface on glass or on the top edge surface edge of a
slumped bowl. It's a large horizontal wheel similar in concept
to a record turntable or potter's wheel. There are two basic
types -- the vibratory flat lap and the rotary flat lap.
The vibratory flat lap (also called a
reciprolap or an automatic vibrating lap), uses silicon carbide or
aluminum oxide grit or polishing powders
to smooth the surface of the glass. This type of machine
automatically vibrates, and can be operated without constant
To use the reciprolap, the machine is first
prepared with a slurry of the desired size grit. (As with most
grinding/polishing activities, the procedure starts with coarse
grits and finishes with finer particles.) Once prepared, a
piece of glass is placed on the lap and the machine is turned on.
It vibrates under the glass, steadily abrading, grinding, and
polishing the piece.
Although relatively little attention is
required while the machine is vibrating, grinding and polishing with
a reciprolap is a time consuming process. Each step of the
process takes a day or longer, with weights often being placed on
top of the glass in order to accelerate the process.
To prevent contamination, the machine must
be cleaned thoroughly between grits. Or, more frequently, a
series of machines is used to complete the process, with each
machine dedicated to a single grit. The entire procedure, from
rough grinding with a coarse grit to final polishing with polishing
powders, can take several days and sometimes even weeks.
Because of the expense of these machines,
the reciprolap is most often used in more industrial or high volume
settings that can afford a series of automated machines.
here for information on the rotary
flat lap, an alternative that grinds and polishes glass using an
abrasive disc (usually diamond).
Copyright 2006 Brad Walker.
All rights reserved.