The daily Cairo bulletin. (Cairo, Ill.) 1878-1???, 1884-12-09
DIAMONDS FOR DRILLS.
An Explanation of the Apparatus by Which
Deep Rock Boring Is Accomplished.

Diamonds are comparatively cheap
nowadays a rock-drill manufacturer
said to New York SIN reporter, "and
the diamond-set bits used in the dia-
mond drills do no. cost as much as they
did,
care genuine diamonds used in these
drills, or are they called diamond
drills because the steel has an extreme
ly hard temper?' the reporter asked.
Diamonds are used in the drills.
They are chiefly one and two carat
stones. AT present they cost about 800
a carat, They are in the rough. The
diamond-set bit is hollow. 1t is a steel
thimble having three rows of diamonds
imbedded in it, so that the edges in one
row project from its face, while the
edges of those in the other two rows
project from the outer and inner per-
iphery respectively. The diamonds of
the aforementioned row cut the path of
the drill in its forward progress, while
those on the outer and inner periphery
Of the tool enlarge the cavity"
"How are the diamonds set in the
bit?"
The bit is of soft steel, in which
holes are drilled. After the diamonds
are fitted the metal is hammered
against them so that they remain
firm"
''Do the diamonds wear out?
"Their edges which come in contact
with the rock get little smooth, and
then they are taken out and reset, so
that fresh edge spresented.
"Have all the hollow drills three
rows Of diamonds?'
"No. Some have only one row, but
these are not very large, The dia-
monds stand out from the steel setting,
so that the steel does not come in con-
tact with the rock" .
"How are the diamond drills work
ed?"
"By rapid rotation varying any,
where from 400 to 1000 revolutions
minute. There are different machines
used for different kinds of drilling. For
deep boring a machine with a double
oscillating cylinder engine is used
mounted on an upright or horizontal
tubular boiler. The machine has a
screw shaft made of heavy hydraulic
tubing from five to seven feet in length,
with deep screw cut in the outside.
The shaft also carries spine, by which
it is feathered to lower sleeve gear.
This gear is double, and connects by
its upper teeth with beveled driving
gear, and by its lower teeth with re-
lease gear, which is friction gear, and
is fitted to the lower end of the feed
shaft, to the top of which gear is
fcathered, fitting to the upper gear of
the screw shaft, which has one or more
teeth less than the upper gear on the
feed shaft, whereby a diilerential feed
is produced This friction gear is at
tached to the bottom of the feed shaft
by friction nut, producing a combined
lilerential and fractional feed, which
renders the drill perfectly sensitive to
the character of the work through
which it is passing, and maintaining a
uniform pressure The drill rod, made
Of heavylapweld tubing, passes through
the screw Shaft and is held firm by a
chuck at the bottom of the screw shaft.
70 the lower end of this tubular boring
rod the bit is screwed, and to the upper
is a watch swivel, to which connection
is made with steam-pump. You can
see by this that the machine is very
simple and not likely to get out OF
order.
The reporter fell into q chair When
he came to, the drill man was saying;
"The screw shaft, being rotated and
ted forward, rotates the drill rod and
bit, cutting an annular channel---n
where do you get thed iamonds for
your bits!' the reporter asked in des-
peration.
They come principally from Brazil.
Some come from Siberia and some
from the south Of Africa the latter,
however, are more CLASSY and are not
so tough as the Brazilian diamonds,
and much more likely to crush under
pressure.