The intelligencer. [volume] (Lexington, Mo.) 1887-1891, 1890-01-11
Asou CIRCULAR SAWS.

How the Plates from which They Are
Made Are Treated and Tempered.
Ordinary circular saws are of all
sizes from six inches to six feet In
diameter. The plates from which they
are shaped come from steel mills in
circular form, almost round, II not
perfectly 80. The first thing TO be
done is to see that each plate is made
q perfect circle. A hole is then cut In
the center, and the teeth are marked
around the rim. The plate is then
taken to a machine on which the teeth
are to be cut. 1t Ii placed upon q pin
at such q distance from the machine
that the edge comes beneath the die,
and the operation OF ~teeth-cutting be-
gins. The steel Is cut cold, each tooth
being made by one blow. All sizes and
descriptions OF dies are necessary, as
the style Of saw and saw-teeth are
many. After the teeth have been cut
the next operation is that Of temper
ing, which Is the most difficult and i'm
portant process In the making of a
saw. Several saws are placed in the
furnace at = time and allowed
to remain until they have reached
the proper temperature, a light
cherry red, when the plates must be
taken from the oven and plunged into
. vat OF whale oil, heated by pieces Of
red-hot iron or steel, which are placed
in the vat one after another until its
contents are properly heated. As each
piece is dropped in. a brilliant flame
leaps from the surface OF the oil, and
continues to burn until extinguished
| by stirring the liquid with q long iron
rod. The large glowing plates are
then cautiously slid into the vat. Leav-
ing the tempering department, the saw
goes back to the main shop to be ham,
mered and Strengthened ready for
grinding. This work is done by hand.
After the plate, which has been more
or less warped during the tempering
process, has been made perfectly
straight again, it is placed in the grind
ing machine. which is u carriage be-
tween two wheels which turn it. and at
the same time press its sides against a
rapidly revolving grindstone. The car
riage is fixed in automatic bearings,
d 10 moved back and forth at the will
Of the operator. 1t usually takes about
two hours to grind a large fve.foot cir
cular saw, though the time varies ac-
/ cording to the kind Of saw that is being
made. The next operation il that Of
polishing. which is done with emery
wheels. To polish alarge circular saw
the plate is secured to a large wheel or
hange, which turns, carrying the saw
with 1t, the workmen meanwhile press
ing an emery ball attached to a handle)
against the side.
The saw must then be rounded
that Is, care must be taken to prevent
one tooth projecting farther than the
others. For this purpose the saw is
placed In q bearing, and made 70 turn
slowly. It 10 then gradually brought
In contact with An emery wheel. the
latter t~arning very swiftly. until the
edge Of every tooth touches the wheel.
The saw Is next sharpened and sub
mitted TO further hammering for the
purpose Of ''truing' and s~traighten-
ing, and is then cased ready for ship
ment.
One important part of tho saw
maker's business is the renov xtion Of
old saws injured in fires. 1t is straight
ened up, tempered over again. and pro-
vided with a new set OF teeth,
This article has dealt only with COM
mon circular saws, the teeth OF which
are not separate from the plate. Other
saws, however, supplied with inserted
teeth OF various kinds. are made in
large numbers. These are all patent
saws, and can be supplied with new
sets Of false teeth as often as necessary
Mechanical News.