The Republican journal. [volume] (Belfast, Me.) 1829-current, 1900-10-11
HUGE GRANITE COLUMNS.
Enormous Masses to he Shaped and Polish
ed in . Lathe,

Enormous Masses to be Shaped and Polish.
ed in = Lathe.
For the Cathedral of st. John the
Divine, in New York city, thirty-two
magnificent granite columns are to ho
supplied, each as high as four story
house, and to shape them a remark ahle
piece of machinery has recently been
constructed in Philadelphia and sent
to the quarries of the Bodwell Granite
Company, in Vinalhaven, Me. IA is
nothing less than turning lathe of nm.
paralleled strength and proportions
A good illustration of the objects and
operation of lathe is found in a shon
where wooden balusters are mannfac,
tured. A stick of wood, three or four
inches square and two or three feet
long, is adjusted in horizontal posi-.
ton, with its ends firmly held bv metal
disks, which are intended to reyolye
rapidly. The stick being thus set in
rotation, workman applies to it the
edge OF chisel, or other cutting tool.
which rests on fixed support, but NAV
be shifted from one end of the stick to
the other. The result of this treat
ment is to make the stick perfectly
round in very short time. Its diane
ter at different points may be varied. if
this is desirable, SO that in one place
there is graceful bulge and in another
slender taper. Lathes are also built
for working metal, and the cutter is
usually shifted automatically by screw
motion, so that the lack of uniformity
which results from hand work is elimi-
mated, and absolute adherence to a
model insured.
The same method is now employed in
shaping long blocks of stone into col
umns like those in front of the New
York Life Building in Broadway. The
stone is suspended horizontally between
the ''head stock. and tail stock" both
OF which can rotate. AS in other lathes,
the power which causes the stone to re-
volve is applied to the head stock. By
arranging suitable cutting tools on the
side the supertluous material is Clipped
off by degrees, and the column is reduc
ed to the desired dimensions as surely,
though, of course, not SO rapidly, as a
wooden baluster.
The finished columns of the Episcopal
Cathedral are to be "a feet long, and
have diameter of feet. When finish
ed, each will weigh 100 tons. But to be-
gin with, a block is quarried out that is
cross sections and weighs about 80 tons.
This burden must be sustained by the
two rotating ends of the marvellous ma
chine recently sent to Vinalhaven. Be-
fore the lathe is put in operation it is in
tended that little of each rectangular
edge shall be taken off from the block
by hand. Eight cutting tools will be adj
justed close to each other, one going a
little deeper than its predecessor Each
is designed to cut off three inches of
stone, so that together they would be
capable of making cut twenty-four
inches in depth. Bya suitable mechan-
ism these cutters are slowly shifted
from one end of the lathe to the other,
so as to traverse the whole length of the
column. But they are set in such a
manner that they cannot make the diam
eter less than six feet.
When column has thus been
brought down to the proper size it still
has rather rough surface. The stone
must now be polished. This second
operation is conducted with the lathe
also, but the rotation is effected at a
somewhat higher rate of speed. There
are two polishing processes. The first,
or rough polishing is done iii a cup
shaped device that has lot Of harden
ed steel shot i'll contact with the NOV
ing surface. In the final operation
sand and emery are employed. y period
of about six weeks is required for each
column. 1t will take nearly four years,
therefore, to get out the whole thirty
two columns.
This machine is S6 feet long and
weighs 1875 tons. 1t is much larger than
any other stone cutting lathe ever be
fore constructed. 1t is driven by a
fifty horse power engine. When en-
gagged in cutting its speed is one and
three-quarters revolutions a minute.
and three when used for polishing.
The change of speed is effected by
gearing. The work of constructing the
lathe was begun in December last, and
it was delivered to the Bodwell Granite
Company in May. But it was not put
into operation until few weeks ago.
New York Tribune.