The south Kentuckian. [volume] (Hopkinsville, Ky.) 1879-1883, 1883-10-04


The word "granite" generally con-
vcys the idea Of roughness, coarseness
and solidity. The idea of finish, smooth
ness and polish does not, in the popular
mind, belong to the material. But most
kinds of granite are susceptible of
beautiful and almost faultless surface
finish. The effect of this finish in con-
trast with the hammered faced granite,
on monuments where a tablet is surface
polished, or lines of lettering are in
brilliant contrast with the dull gray of
the unpolished stone, is very fine, espe-
cially so when the shafts of columns are
thus finished, the bases being hammered
and the capitals carved. As this finish
can now be obtained by machinery at a
low cost, the possibilities of obdurate
granite for ornamental rs well as for
building purposes have been greatly en-
larged.
Granite columns, vases and similar
cylindrical ornaments are polished in a
lathe. This differs but little from an
ordinary machinist's lathe, except that
u continuous bed is not necessary to hold
the lathe heads, that the spindle of the
foot stock revolves as well rs that of the
heal stock, and that no tool carriage
and appurtenances are required The
head-stock is furnished, like that of the
ordinary back-geared lathe, with back
shaft, on which is the driving pulley, or
the cone of step pulleys, from which the
spindle is driven by means of q gear and
plnion, the surface speed of column
under process of grinding and polishing
/ ing from 230 to 240 feet per minute,
lg to twelye-inch column about
sevGnty-scven turns per minute and to
a thirty-six-inch column about twenty
five turns per minute.
To center and swing a column in the
lathe the stone has square recess cut
in each end, into which is fitted block
of cast iron with round hole through its
center The place of this block is found
by means of a cross of wood with slid
ing arms on each of the four limbs of
the cross, the arms projecting over the
surface Of the column longitunalty, and
when equidistant from the center de-
noting the place of the center block, so
that the true center of the column or
shaft is found, just as it is on an iron
shaft, from the circumference. The iron
block is secured in place by a running
of Babbit metal, or similar unshrink-
ing compound, around It. The centers
of the lathe spindles fit the holes in the
blocks, and when swung to the lathe
the column is rotated by means of a lug
or dog on the face plate engaging with
one seated in the end of the column,
Back of the lathe is wall of plank
against which rest the ends of num-
ber of iron blocks, three or four inches
diameter, long enough to project over
the column and TO have their rear ends
resting against the bulkhead or wall.
Their under sides are concaved TO en-
brace the column one-fourth of its diam
eter or less, and as the motion of the
column in grinding is reverse to that Of
the ordinary lathe, the blocks are held
against the wall by the rotation of the
column. These blocks are arranged
closely side by side, and when the col.
umn Is first worked its irregularities oi
cniseling and unevenness of contour
make these blocks play up and down
like the movement of pianoforte keys
under the fingers of performer, But
as the grinding progresses this irregular
movement becomes a very slight undu
lation, pleasant to see.
A trough runs under the column it.
entire length, and from it an attendan
shovels beach sand and water on tn,
revolving column, the blocks with thei
concave faces acting as grinders, jus
as the hinge clamps Of the machinist!
are used in polishing a turned shaft
And like the clamps, the series o
blocks are occasionally pushed along
one-half of their width to avoid ring,
of roughness. This quartz sand is uset
until all the bruises, ''stunts," ant
chisel marks are taken out, and tn,
surface shows uniform color. Ther
the trough is cleaned and emery of tn,
numbers forty to sixty, according to tn,
quality of the stone, is weighed out il
the proportion of about half pount
to every superficial foot; thus column
of ten feet in length by three feet diane
ter-ninety superficial feet-would re
quire from forty-five to fifty pounds
This is all weighed out at one time
! and is never added to during the entir,
process. Mixed with water, it is fed Il
the grinders by the shovelful, over ant
over, until the grinding is entirel,
completed. The reason for this il
evident from the fact that. in using
the emery becomes ground up ant