SAWING 
MILLS. 
709 
. are put in between the blades of the saw at the upper and 
lower ends, and the spaces being thus filled up, they are 
bound tight by screws, which are tapped into the sides of 
the saw-frame. As the tension of the different saws would 
be very uncertain, if it depended merely upon driving the 
wedges of their shackles by a hammer, the inventor has ap¬ 
plied a very ingenious kind of steel-yard, to strain each of 
the saws in its turn. It consists of the following' parts: a 
strong axis is extended across the fixed frame, in which the 
saw-frame slides, and above the top of this frame; from one 
side of this axis a lever proceeds, which has a weight fixed 
at the end, and from the opposite side of the axis proceed 
two short levers, which are connected by links with a strong 
cross-bar, situated just over the upper cross-bar of the saw- 
frame, when it is at its greatest point of elevation. This 
steelyard cross-bar has a link or shackle upon it, which can 
be united by a key with any one of the shackles upon the 
upper tross-bar of the saw-frame, which shackles are, as be¬ 
fore-mentioned, united by their hooks with the upper end of 
their respective saws; by this means the lever, with its 
weight, becomes a steelyard to draw up any one of the saws 
with a determinate force, and it can be applied successively 
to all the different saws. In using this apparatus, the band 
or strap of the crank-shaft is cast off, to stop the motion of 
the saw-frame; the crank is turned round, to elevate the 
frame to the highest point; two wedges are then put in be¬ 
tween the top of the saw-frame and a fixed part of the sta¬ 
tionary frame, and this holds the saw-frame fast whilst the 
steelyard is applied, otherwise it would tend to draw up the 
frame, and strain the crank and crank-rod. The sharp saws 
are now put into the saw-frame, by hooking them upon the 
lower cross-bar thereof, and uniting the upper hooks to the 
the shackles on the upper cross-bar: the pieces of wood are 
next put between the saws, according to the gauge of the 
wood which is intended to be sawn, and bound fast by the 
screws, as before mentioned. The loaded end of the steel¬ 
yard is now lifted up by a rope passing over a pulley, and 
the link upon the cross-bar of the steelyard is united with the 
shackle of one of the saws by means of its keys; then suf¬ 
fering the steelyard to descend, it stretches the saw: the 
wedge of the shackle for the saw is thrust in by the hand as 
far as it will go, and thus retains the saw at the tension to 
which the steelyard has strained it. The shackle of the steel¬ 
yard is then disengaged from the saw and removed to the 
next, and thus, in turn, all the saws are equally strained, a 
circumstance which is of great importance, because any saw 
which is more slack than another will be liable to bend and 
cut crooked, when the grain of the wood tends to divert it 
from its true direction. 
The carriages of this mill are very admirably contrived to 
hold the trees firmly, and to fix them in a little time : they 
are advanced, as the saws cut, by a rack and pinion, with 
a ratchet-wheel; and the click of the ratchet is moved by 
means of an excentric wheel, or camm, upon the axis of the 
crank. There is also a contrivance, by which the saw- 
frame is allowed to retreat a small quantity in its ascent, so 
that the teeth of the saw will be quite clear from the wood, 
when they return, that is, when they ascend, and do not 
cut. Mr. Brunei has directed the execution of several other 
saw-mills upon the same principle, particularly a very large 
one in the dock-yard at Chatham. 
Circular Sawing-Mac/iines .—Circular saws, or saws of 
a circular form, which cut during a continuous rotatory mo¬ 
tion, have been used for cutting the teeth of watch and clock 
wheels since the time of Dr. Hook. They have been long 
used in Holland for cutting veneers, and they are said to 
have been introduced into this country by General Bentham. 
Mr. Taylor of Southampton, and Mr. George Smart, had 
the merit of introducing them very early; but we do not 
know the exact dates. 
A circular saw is nothing more than a circular plate of 
steel, having teeth upon its circumference, and made to 
revolve upon an axis with great rapidity, by means of bands 
or straps. The saw itself may move either on a horizontal, a 
vertical, or an inclined plane; and as the timber may be 
Vo l. XXII. No. 1534. 
laid upon a plane inclined in any given direction, it may be 
sawn in lines making any angle whatever, or at any given 
distance from one another. When the saw is fixed at a cer¬ 
tain angle and at a given distance from the edge of the 
frame, all the pieces of wood may be cut exactly of the same 
size, by pressing them against the edge as the saw is cutting 
them. The following is a description of the circular saws 
at Rothiemurchus in Inverness-shire. 
There are two kinds of saws made use of in the Rothiemur¬ 
chus saw-mill; circular saws and upright ones. A circular 
saw is a thin round plate of steel, toothed on the circumfer¬ 
ence fixed on a revolving axle. An upright saw is the com¬ 
mon saw made use of by sawyers, fixed in a frame moving 
vertically. In both cases, the log to be sawn is fixed to a 
frame, which is moved against the saw. Each of these con¬ 
structions has peculiar advantages. The upright saw, it is 
evident, cuts only in descending; there are also two points 
in every stroke at which it is stationary—the one when it is 
at its height, the other when at its lowest. A large propor¬ 
tion of the time of each stroke is thus consumed without 
effect. A circular saw cuts during the whole of its revolu¬ 
tion ; and it is found that a much greater velocity can be 
given to a circular motion, which is equal and constant, 
than to an upright one, which is necessarily unequal. A 
circular saw is thus much more expeditious than an upright 
one. It is, however, much more limited in its application, 
>as it can only work in wood of less depth than the radius 
of the saw. The size of wood is further controlled by the 
thick plates of metal which are made use of to fix the saw on 
its axle. These flaunges, as they are called, it is found by 
experience, require to be about one-third of the diameter of 
the saw. Besides this, the size of the saw itself is controlled 
by the thickness required to give the plate sufficient stiffness. 
A circular saw, too, one-eighth of an inch thick, would 
occasion much loss in saw draft. In this mill no saws have 
ever been used above three feet diameter. 
The application of upright saws is controlled only by the 
length of stroke given to the saw frame and its size; the 
stiffness of the saws is given by stretching them tightly be¬ 
tween the upper and lower ends of the frame, and is there¬ 
fore in a great degree independent of the actual size of 
the saw. 
The intention in this mill is to saw by circular saws where 
they would not occasion too great a loss in saw draft; and 
in this case only, to saw by upright ones. 
The circular saws run about 1000 turns per minute, and 
will cut 10 inches deep on 3-16ths of an inch of saw draft. 
The upright saws make about 120 strokes per minute, and 
will run on rather less saw draft. 
The circular saws will cut a 12-foot log in less than a 
minute; the upright saws in equally fine work, will not cut 
above 15 inches in the same time. 
An improvement in the mode of fitting up circular saws 
was made by Mr. Maudslay. When the pivots at the end 
of the axle were conical, or when there were conical hollows 
on the end of the axles working upon fixed cones, the oil 
was always carried up the cone by the centrifugal force, and 
the sharp point being left without oil, soon heated, and 
caused the metal to become soft. In order to avoid this, 
Mr. Maudslay made his saw spindles with double conical 
sockets, and the oil was introduced by a small hole into the 
smallest part of the double cones where they join. By this 
means the centrifugal force draws the oil into the fitting. 
In order to prevent thin circular saws from bending, or 
buckling as it is called, they are confined between two fiat 
circular plates: but in place of doing this, the bending is 
now confined to a more narrow ring near the rim of the saw. 
By this contrivance, the saw revolves with such truth and 
accuracy, that it is fit for the nicest operations, such as cut¬ 
ting the teeth of the finest cones. It is considered advan¬ 
tageous to soften circular saws when the teeth require sharpen¬ 
ing, and to temper them only to a yellow colour. See Dr. 
Brewster’s Journal of Science, No. III. 
SAWLEY, a parish of England, in Derbyshire; 9J 
miles east-south-east of Derby. Population 823. 
8 S SAWLEY, 
