January 4, 1918.

THE COLLIERY GUARDIAN.

CARE AND MAINTENANCE OF CUTTER
PARTS.*

By Adolph F. Fobs.

Bits.

Most mine operators who use chain coal-cutting
machines have come to realise the importance of sharp
bits to the successful operation of these machines.
Sharp and properly shaped bits tend to decrease the
load on the machine, and the saving in power alone
justifies careful attention to this matter. Along with
the decrease in load comes increased life of parts, and
in general it is of the utmost importance to keep a coal-
cutting machine supplied with sharp bits in order to
ensure continuous and economical operation.

The main points to be considered are: (1) Correct
bit shape and method oh forging; (2) method of tem-
pering ; (3) most effective method of distribution.

As to the shape of the bits, this depends largely upon
the design of the chain block and upon the nature of
the coal being cut. The bit should be forged so that it
does not drag its way through the kerf but rather does
it£ work at a cutting angle. There is a possibility of
getting the bit forged so that it has a tendency to hang
up or dig in too deeply, but, on the other hand, the
tendency usually is to forge the bit too straight, and
this introduces the dragging action just spoken of.

The shape of the bit best suited to the conditions
under which it works must be determined at the
individual mine. When once this shape is determined,
it is a good plan to have a few correctly formed bits kept
in a place where they can be referred to as samples from
time to time and thus prevent any gradual deviation
from the bit shape which has once been determined to
be the best suited to local conditions. Whether the
cutting bit should be chisel- or pick-pointed or some
intermediate shape must also be determined for each
particular installation. If the coal breaks up freely
and can be considered brittle, it is usually best to use
pick-pointed bits exclusively, as then the cuttings will
be coarser. Frequently, also, the load on the machine
will be decreased. Where the coal is tough and woody
it is often advisable to use a certain number of chisel
bits interspersed among the pick bits so as to ensure a
kerf that does not leave projections that engage the
body of the chain block or cause the set-screw heads to
wear round.

At mines where only two or three cutting machines
are in use, the number of bits to be sharpened does not
often justify the installation of a power forge hammer.
Instead, the blacksmith forges the bits by hand. This
hand forging is a slow and expensive process. One of
the evils of hand forging is that the blacksmith is
tempted to get the bits as hot as possible in order to
save hammering. This excessive heating of the bits
reduces the quality of the steel and should be avoided.
Although a hand-shaped bit is oftentimes more care-
fully finished than a machine-sharpened bit, still the
disadvantages are so great that even in small opera-
tions it usually pays to instal some kind of bit-forging
hammer.

The forge used in heating the bit is also worthy of
attention. Many operators buy good bit steel and then
reduce it to poor quality before it leaves the forge,
simply because they insist on using the coal they produce
at the local mine. Coal with impurities should not be
used, but instead crushed coke may be employed.

Tempering Process.

Tempering is more or less of an art, and it is difficult
to lay down any fixed rules or prescribe any certain
process and say positively that they are the best. While
some blacksmiths have success with one method of
tempering, others use a different way entirely. I will
consequently outline a few of the most popular methods
and suggest that these be tried out. Thus by experi-
ment it may be determined which is the best suited to
the local requirements.

Plain-Water Tempering.—The bit should be heated
to a cherry red and then quenched in cold water. Bits
tempered in this manner are good where the cutting is
comparatively hard and where impurities are occasion-
ally encountered. Bits tempered in plain water wear a
little more rapidly than those tempered in salt water,
but are not as liable to break.

Salt- Water Tempering. — When the bit has been
brought to a cherry red. it should be quenched in a
solution of common salt in cold water. This method
- renders the point hard and brittle, and is very good for
comparatively soft coal which is free from sulphur
streak or other occasional impurities.

Oil Tempering.—With the oil-tempering method, the
bit is not rendered quite as hard as by either the plain
or the salt water method, but the bit is very tough.
When the steel is the usual cherry red, it should be
quenched in oil. Although some blacksmiths drop the
whole bit into the oil keg, it is usually a good plan to
provide some sort of a rack so that only the point of
the bit dips into the liquid.

.Sand or Clay Tempering.—With this method, .a box
containing wet clay or sand, or ca mixture of the two,
is used to temper the bits. After the bit has been
correctly forged, it is heated to a cherry red, after
which the point is stuck into the wet clay and the bit
is left there. When the point is inserted in the wet
clay it is chilled and hardened ; then, as the heat from
the bit works into the clay, the extreme hardness of
the point is drawn slightly and the bit is rendered
tougher and somewhat softer than with the plain-water
tempering.

Soap-water Tempering.—A solution of cheap laundry
; soap in soft water gives good tempering results and is
comparatively inexpensive. One cake of soap to
25 gals, of water is sufficient, and where the water is
too hard to lather freely, a little washing powder should
be added. When starting the tempering operation, the
solution should be heated to the boiling point, after
which the cherry-red bits may be thrown into the soap •
water. The hot bits keep the water at the proper
temperature. This soap-water process ensures slow
cooling and an evenly tempered bit. It is usually a

* Coal Age.

good plan to have a large wire basket or bucket
immersed in the tub of soap water, as in such a case
the bits can be easily removed from the tub when
. through tempering.

Tempering Solution.—There are numerous tempering
solutions on the market for which certain merits are
claimed. They are mostly used in a similar way to the
soap-solution method just explained.

In order to encourage the machine runner to change
bits before they become dull enough to unduly load the
machine, it is important to employ some regular
schedule whereby the runner is sure constantly to have
a sufficient supply of sharp bits. Many mines find
it profitable to detail one man to be responsible for this
bit distribution. A system that has been found effective
is to provide each machine with four or five small iron
bit boxes, which can be made by the local blacksmith.
The material should be | or T3K in. plate iron, and the
construction of the boxes should be rugged. The box
should be provided with a cover, and it has been found
satisfactory to use a key-ring arrangement as a lock.
Each box should be given a number that will identify it
with the machine upon which the bits contained in the
box are used.

At some convenient point near the shaft bottom
there should be located a bit-distributing station. As
soon as a box of sharp bits is received at the shaft
bottom, the box should be placed in a certain compart-
ment in this bit-distributing station. This compartment
should be marked according to the machine that the
bits are intended for. The motorman or trip-rider should
visit this distributing station each trip, and be sure to
take whatever boxes are marked for the territory to
which he is going. Other details in connection with bit
distribution will have to be worked out according to
local conditions, but under no circumstances is it an
economical plan to distribute the bits promiscuously in
open kegs.

Considerable work and great difficulty may be expe-
rienced in getting a bit-distributing system started,
but after it is once going it should take care of itself
and really be a money saver to the company.

Chains.

The part of a coal-cutting machine which really does
a large portion of the hardest work and which is most
likely to receive the least attention is the cutter chain.
The following suggestions refer to the proper care and
maintenance that should be given the cutter chain and
associated parts in order to ensure continuous and
satisfactory operation.

The Chain Tension.—The question of the proper chain
tension is largely a matter of judgment resulting from
experience with the use of a coal-cutting machine.
Nevertheless, a somewhat fixed rule can be adopted in
regard to determining the proper tension. A satis-
factory rule followed by many of the larger operators is
as follows:—

After the machine has cut a 30 ft. room, test the
chain tension by pulling the chain out of the guide at
the right-hand opening in the side of the underframe.
The chain is at the proper tension when it can be
brought out to a position flush with the outside of the
cutter arm.

In case the cutting machine is not provided with an
opening in the side of the underframe, the testing of the
chain tension is a more difficult matter. By taking
hold of the chain lugs near the centre of the arm and
moving them up and down, one is not able to accurately
determine whether the chain is at the proper tension.
It is a common occurrence to see a mine electrician or
machine inspector step up to a coal-cutting machine,
take hold of the lugs and imagine that he is testing the
chain tension. As a matter of fact, the lips on the
chain guide hold the chain in the arm so that testing
its tension near the middle of the arm is more than
likely to be deceiving.

When the cutter chain is allowed to run too tight, it
introduces an unnecessary friction load on the machine
accompanied by considerable heating of the cutter head
and other bearings, and rapid wear of these parts is sure
to result. On the other hand, if the chain is permitted
to run too loose, it becomes a difficult matter to control
the machine; that is, the cutter arm either climbs or
else digs down into the bottom. Spreading and rapid
wear of the cutter-arm guides is one of the results of a
loose chain.

Furthermore, when the chain is loose, it does not
enter the cutter arm properly after leaving the sprocket,
and the chain is liable to become fouled. When the
chain is loose it has a tendency to weave; that is, one
block or bit tries to follow the cut made by the pre-
ceding one, and eventually a cutterjbit comes along that
will be required to cut more than its share. The load
thus imposed often causes chain breakage and severe
overloading of the whole machine. This weaving is
also frequently the cause of the rapid wear of the set-
screw heads. Thus, it is clear that it is of the utmost
importance to keep the chain at the proper tension.

Oiling Chains.—Aside from the regular lubrication
with a heavy oil just before or after cutting a room, the
chain should be oiled once or twice a day with a lighter
oil, allowing this lubricant sufficient time to reach the
working joints of the chain. Before oiling the chain,
it is a good plan to let it run a few seconds so that the
coal cuttings and dust will be thrown out and not get
clogged up with the oil when it is applied. Several
schemes have been developed which provide a means
for continuously oiling the cutter chain while the machine
is crossing the face. These, however, do not seem to
work out satisfactorily, owing, no doubt, to the fact that
when the chain is in rapid motion the oil is almost
immediately wiped off, and only a small portion of it
accomplishes any useful lubrication.

A sprocket-type cutter head should always be pro-
vided with wool waste to ensure gradual feeding of oil
to the sprocket when cutting. When this waste is
removed or renewed a convenient opportunity is afforded
for extracting any coal dust or dirt that may have
gotten in the cutter-head cavity.

Tightening Clamp Bolts.—On a machine which is so
constructed that the cutter arm is clamped to the main
frame, it is important that the clamp bolts be kept

tight; otherwise, the plane of the cutter arm may be
out of line with that of the sprocket. One of the results
of a loose cutter arm, therefore, is that the chain does
not ride the driving sprocket correctly and fouling
of the chain is almost sure to result. A machine with
a loose cutter arm is also rather difficult to control under
the coal.

Bit Gauges.—The machine runner should always use a
bit gauge when setting bits, so that these parts all take
hold uniformly, and the cutting load is thus properly
distributed over the chain. If a bit gauge is not used,
and the runner sets the bits by guess, some are almost
sure to be out farther than the others. A long bit con-
sequently does more than its share of the cutting and
becomes dull before the others. These dull bits cause
a heavy load to be imposed upon the machine during the
rest of the cut or until they are renewed. The proper
length of bit gauge is such that the cutter arm cuts with
ample clearance until the time comes to reset the bits
because they have become dull.

Repairing Chains.—When rebuilding a chain do not
put new and old straps together at random, but rather
match up the straps so that any pair of straps share the
load equally. In other words, use two new or two old
straps together.

When repai ring a chain whileon the machine, make sure
that something solid is placed under the cutter head so
that the chain rivets will be drawn up tight. After
putting a new rivet in the chain, its head should be cut
off flush with the straps. High rivets cause heating of
the chain and rapid wear and possibly spreading of the
chain guides.

When riveting a cutter chain with a hand hammer,
care must be taken as much as possible to only hammer
the rivet and to avoid striking the strap any more than
is absolutely necessary. The reason for this is that
mining-machine manufacturers are case-hardening their
cutter chains, and the hammering on the straps is liable
to crack the portions that are thus hardened.

It is bad practice to let the chain continue in operation
with several dead lugs in it. As soon as there are two
chain blocks that for some reason or other are unable to
hold cutter bits, it is a good policy to replace them.
The absence of any bit generally causes the next one of
the same position to do twice the intended amount of
work, and therefore the whole mechanism is propor-
tionally stressed an excessive amount.

In general, the chain is really the toolholder of a coal-
cutting machine, and as such is worthy of close attention
in order to ensure continuous satisfactory operation.

AIR REQUIRED TO OPERATE
AIR-LIFT.

By A. W. Allen.

. The free-air requirements given in the appended
table are only roughly approximate, and in view of the
wide elasticity of operation of this class of pump any
greater precision has been considered unnecessary.
The figures given are based on theoretical calculations,
plus a wide margin to allow for work in ordinary
installations. If care is taken in the design of the lift,
the amount of air actually required will be found to be
below the estimated volume; but it was thought
advisable to allow an ample margin, as excess of air is
used in so many installations as a remedy for defective
design. On the other hand, it is almost impossible to
estimate with accuracy, in a case in which there is much
constriction at the intake, bends or elbows in the rising
main, or in which the air inlet is nozzled in a mistaken
idea that the water is forced up with the pressure of the
air.

Volume of  Lift Ft. sub-		Air Required to Operate Air Lift.					
		2 in. 21 in.	UI ULU JJipU.  3 in. 81 in. 4in.			5 in.	6 in.
Ft.	merged.	r—		Cubic feet of air per minute. -						>
5 .	.. 7 5 ...	13 ... 22 ..	. 31 .	.. 45	... 56 ..	. 90 ..	. 126
10 .	.. 15’0....	15 ... 24 ..	. 34 .	.. 49	... 61 ..	. 98 ..	. 137
15 .	.. 22’5 ...	.16 ... 26 ..	. 37 .	.. 53	... 66 ..	. 105 ..	. 147
20 .	.. 30'0 ...	17 ... 28 ..	. 39 .	.. 56	... 70 ..	. 112 ..	. 157
25 .	.. 37'5 ...	18 ... 30 ..	. 42 .	.. 60	... 75 ..	. 120 ..	. 167
30 .	.. 4>'O ...	19 ... 32 ..	44 .	.. 63	... 79 ...	. 127 ..	. 177
35 .	.. 52'5 ...	20 ... 33 ..	. 47 .	.. 66	... 83 ...	. 133 ..	. 18Q
40 .	.. 60'0 ...	21 ... 35 ..	. 49 .	.. 70	... 86 ..	. 139 ..	. 194
45 .	.. 67'5 ...	22 ... 36 ..	. 51 ..	.. 73	... 90 ...	145 ..	. 202
50 .	.. 75’0 ...	22 ... 37 ...	. 52 ..	. 75	... 93	150 ..	. 210
5 .	.. 10'0 ...	10 ... 17 ...	. 24 ..	. 35	... 43 ...	. 69...	. 97
10 .	.. 20'0 ...	11 ... 19 ...	. 27 ..	. 39	... 48 ...	. 77 ..	. 107
15 .	.. 30'0 ...	12 ... 21 ...	. 30 .	. . 42	... 53 ...	85 ..	. 117
20 .	.. 40'0 ...	13 ... 23 ...	. 32 ..	. 45	... 57 ...	. 91 ..	. 127
25 .	.. 50'0 ...	14 ... 25 ...	. 35 ..	.. 49	... 61 .;.	98 ...	.136
30 .	.. 600 ...	15 ... 26 ...	37 ..	. 52	... 65 ...	104 ..	. 145
35 .	.. 70'0 ...	16 ... 28 ...	39 ..	. 56	... 69 ...	Ill ..	. 154
40 .	.. ao-o ...	17 ... 30 ...	41 ..	. 59	... 73 ...	117 ...	. 164
45 .	.. 90'0 ...	18 ... 31 ..	. 43 ..	.. 62	... 77 ...	. 123 ..	. E3
50 .	.100'0 ...	19 ... 32 ...	. 45 ..	. 65	... 81 ...	129 ..	. 182

The figures given cover submergences of 60 iper cent,
and 66 per cent., the point of maximum efficiency for
lifts up to 50 ft. being probably somewhere between the
two. Flexibility, however, is an advantage, and it is
often found desirable to sacrifice efficiency and decrease
the percentage of submergence. ‘ For a constant length
of rising main, the amount of free air required decreases
as the submergence increases, and increases as the lift
increases. The amount of air used does not materially
vary with the specific gravity of the fluid being lifted
other than in the exceptional case in which excessive
velocity in the rising main and correspondingly high
air volume are necessary to prevent the settlement of
solids. In this case the air lift is not a suitable apparatus
for the purpose.—Engineering and Mining Journal.

A fire at the pithead of Hafodybwch Collieries, Ruabon,
caused serious damage, and threw the miners out of work.

Proposed Nationalisation of New South Wales Coal
Mines. — A cablegram states that the New South Wales
Government is considering the question of the nationalisa-
tion of all the coal mines in the State. On October 3 last
it was announced that the New South Wales Government,
which had taken over the control of the coal mines at the
beginning of the strikes, intended to retain control for a
considerable time, paying the owners a certain amount on
each ton of coal produced.