AGRICULTURAL EXTENSION SERVICE
UNIVERSITY OF FLORIDA
SMALL POWER TOOLS
FOR PRUNING CITRUS
A. H. KREZDORN, P. J. JUTRAS, D. W. KRETCHMAN
Citrus Experiment Station, Lake Alfred, Florida
Since it is hardly possible to describe them otherwise,
certain tools and equipment are mentioned by name in
the material which follows. This does not imply endorse-
ment of these tools, or lack of endorsement of other makes
which now exist or may be developed later.
Mechanical hedging of citrus trees was made possible by the
development of the hedging machine at the Citrus Experiment
Station. However, these machines are expensive and they can-
not be used for selective pruning or where trees are planted on
beds and the groves are traversed by deep ditches.
Since the development of the hedging machine, various manu-
facturers have produced small power pruning tools that are ex-
tremely versatile and can be used effectively for hedging and
other types of pruning.
Fig. 1.-A gasoline engine-powered chain saw (Homelight Division of
GASOLINE ENGINE-POWERED TOOLS
Gasoline engine-powered tools have the engine and the cut-
ting mechanism mounted together as a single unit. There are
2 general types, the chain saw (Figure 1) and the reciprocating
saw (Figure 2). Both have the disadvantages of excessive weight
and the inability to cut the small branches and twigs that make
up the bulk of pruning work. Thus, they lack pruning versa-
tility. But because they are so useful for grove operations, such
as dead tree removal and buck-horning, they unquestionably have
a place in citrus operations.
Fig. 2.-A gasoline engine-powered reciprocating saw (Wright Power
Saw and Tool Corporation).
ELECTRICALLY POWERED TOOLS
Available electric equipment includes the chain saw and the
The electric chain saw is not widely used by Florida citrus
growers. It is light in weight, but early models were not as
durable as their gasoline counterparts. Recent models have
proven more rugged. The electric cord connecting the saw to
the generator, as with all remote powered equipment, is some-
what cumbersome. All electrical equipment should be grounded
according to Florida Industrial Commission requirements. Other-
wise, the characteristics of the electric model are similar to those
of the gasoline type.
The Kwik Kut electric saw (Figure 3A), while having its
limitations, has proven 1 of the most versatile types to date.
It consists of a high speed (10,000 rpm) circular saw blade and
a gear head mounted on an aluminum pole having a driveshaft
B? C Db
Fig. 3.-Motor and trigger (bottom) and gear head (top) of (A) Kwik
Kut electric saw; air flow controls (bottom) and motors (top) of (B) small
Kwik Kut air saw; (C) small and (D) large Ackley air saws. Turning
knurled knob (a) locks the air control lever on or off; pushing up collar (b)
increases speed from moderate to high; holding lever (c) half-way and full
down operates saws at moderate and high speeds respectively. Handles are
removed for adding or changing extensions by depressing lock pin (d);
unscrewing collar (e); or loosening clamps (f).
down the center and a motor and trigger on the lower end. Poles
with enclosed driveshafts are available in lengths up to 6 feet
and are easily interchangeable.
Fig. 4.-Simple but effective pruning rig constructed at the Citrus Ex-
periment Station for hedging. Either air or electric equipment can be used
with the power source mounted on a trailer or on the tractor drawbar.
Height of rear platform is adjustable.
The saw has proven very durable. It has a great deal of
power and makes very smooth cuts. Limbs 4 to 6 inches in
diameter can be removed by undercutting and working around
the limb. Small and moderate size limbs can be cut through in
a fraction of a second, either as selective or as hedging cuts.
The saw was introduced into Florida just prior to the 1957-58
freeze and most were first used for pruning cold-damaged trees.
Since then, however, many growers have constructed movable
platforms or towers of various types from which they carry out
the entire hedging operation (Figure 4). There are no adequate
figures on the cost of hedging in this manner, but operators
using both hedging machines and the electric saws report that
the costs are about equal. This is apparently due to added costs
resulting from mechanical breakdowns of the hedging machine.
Much depends on the ingenuity in constructing the platform
and the organization and efficiency of the operators.
The circular saw is also widely used to dress-up the rough
cuts of the hedging machine and to prune the tops of tall trees
that the hedging machines do not reach. An 8-inch blade is
used most commonly for hedging while the 6-inch blade can be
used effectively for removing water sprouts.
Fig. 5.-Pruning rig constructed by Florence Citrus Growers' Associa-
tion for hedging, using high speed electric circular saw. Two men can
prune simultaneously from the same platform. It is more efficient and safer
to have the pruner in front of the driver.
Functionally, circular saws are not perfect for removing a
large limb attached at a narrow angle because the gear head
at the back of the blade will not fit into the narrow crotch. In
such cases the limb must be cut through several times before
a flush cut can be made. When removing small limbs, as in
hedging, a short chopping stroke is made; but, if used in this
manner on large limbs, damage to the drive mechanism may
result. While classed as a light saw (121/2 pounds) and quite
well balanced, the electric circular saw is too heavy for continu-
ous 1-man operation.
The biggest drawback, in most growers' minds, is the in-
herent danger to the operator and the helper of an unprotected
circular saw turning at 10,000 rpm. This danger is undeniable
and the saws must be treated with respect and care. However,
just as is the case with such dangerous materials as parathion,
they will continue to be used because with proper precautions
they can be operated safely and effectively. As with all high
speed circular saws, this tool should never be operated without
a face guard to protect the eyes from sawdust and small pieces
COMPRESSED AIR-POWERED TOOLS
The compressed air circular saw is run by a small air motor
mounted just behind the blade on the end of a hollow tube. Air
coming through the tube operates the air motor that turns the
blade. The primary mechanical difficulty lies in foreign material
getting into the motor and ruining the vanes and bearings. The
motor is lubricated by an oiler attached between the air outlet
of the compressor assembly and the hose. The flow of oil must
be adjusted properly. Excessive as well as insufficient oil can
The air saws themselves cost about the same as the electric
types, but for comparable power and cutting ability the cost of
an adequate air compressor is appreciably more than for a
The main advantage of the air equipment is its light weight
(51/2 to 71/2 pounds) and good balance. The motors are simple
to repair. There is neither a long driveshaft nor a gear head to
cause trouble, as is the case with the electric models. Easily
added extension tubes are available.
The Kwik Kut is 1 make available (Figure 3B). The handle
containing the air-control lever is swiveled, allowing the saw
to be easily turned, and a 2-speed air flow control permits both
moderate and high speeds. As in the electric model, the blade
continues to revolve after the power is shut off, which poses
a hazard but reduces the power requirements somewhat. Also,
Fig. 6.-Pruning with high speed air chain saw on 12-foot extension. Note
size of cut made at a and flush cut made at b. Saw is 9 inches long.
this machine has no safety feature to prevent the saw from
being turned on accidentally.
Two motor sizes are available and each will handle both
8-inch and 6-inch blades. The larger motor is more powerful,
having about the same speed and power as the electric model,
but the smaller saw requires less air.
The Ackley circular air saw (Figure 3D) is a very powerful
saw. It operates at a lower speed (5,000 rpm) than the Kwik
Kut but requires a larger volume of air. The blade stops re-
volving soon after the air supply is cut off and the control lever
can be locked either "on" or "off." These are important safety
features. The shaft can be quickly extended up to 12 feet.
However, it is very unwieldy at this height. It will take 9-, 8-,
and 6-inch blades.
An Ackley circular air saw with a smaller motor (Figure 3C)
and a 2-speed air flow control regulator for both moderate (5,000
rpm) and high speeds (12,000 rpm) is also available. It has a
5-foot tube and the same safety features as the large model,
but no provision for extension tubes.
All high speed circular saw blades must be kept sharp. Heavy
cutting requires daily sharpening. For lighter touch-up work
and re-hedging the blades may be used up to a week without
sharpening. Sharpening should be done by machine to keep
the blades balanced.
Another recent development in the air tool line is the Ackley
chain saw (Figure 6). This tool has the same air flow controls
and tubular aluminum extensions as the large Ackley circular
The chain saw is 9 inches long and can cut larger limbs than
the circular types. It is narrow, which permits its use in rela-
tively sharp-angled crotches, and its comparatively high speed
produces a satisfactorily smooth cut. It cannot be used for
A tool used for similar purposes is the Miller-Robinson re-
ciprocating saw (Figure 7). This saw cuts more slowly than
the chain type, and it is limited to smaller limbs. On the other
hand, it makes a smoother cut, will fit into very narrow crotches,
and requires much less air than the chain type.
The remaining type of air tool is the lopper (Figure 8), of
which there are a large number of makes and models. These
are widely used in Florida and are too commonplace to warrant
detailed description. Loppers are particularly adapted to the
selective removal of branches, but they are limited to those of
moderate size. Attempts to use loppers on larger limbs result
in an undesirable crushing at the edges of the cut. These tools
are used also for hedging but, because only selective cuts can
be made, the speed of the operation is relatively slow and the
operation is costly.
It is important that adequate power units be selected. Under-
powered equipment does not perform efficiently. Furthermore,
the capacity of the power source decreases with use.
It is usually simple for the grove manager to decide on the
size of a generator assembly, as this will depend on the number
of electric saws operated from the generator and the power
rating of the individual saws. For example, 2 circular electric
saws each rated at 750 watts would operate satisfactorily from
a 2,000-watt (2 kilowatt) generator with a factor of safety of
500 watts (FS 1.33). Universal motors, used on most electric
tools, take DC or AC current and do not require high generator
overload capacity for starting. A DC generator with manual
starting is nearly ideal for this kind of work. It is lighter and
less costly than an AC generator on a per kilowatt basis, but cost
of operation is about the same.
With air tools, a basic knowledge of air equipment is neces-
sary to properly select the compressor. Air tool manufacturers
specify the pressure range under which the equipment will best
perform, together with the volume of air consumed in terms of
cubic feet of free air per minute (such as 150 to 170 psi and
25 to 30 cfm of free air). Compressors are usually rated on a
piston displacement basis (such as 45 cfm). The amount of
free air delivered by a compressor will range from 50 to 90%
of the piston displacement. Be sure to ascertain the free air
delivery rather than the piston displacement.
Even with a compressor designed to meet the requirements
of the tools, the operator must learn to use them correctly. If,
for example, the circular air saws are run continuously, the
pressure may drop below that required to operate them at opti-
mum speeds. Operating the saws in short, intermittent spurts
conserves air and the pressure builds up during the off period.
Fig. 7.-An air-powered reciprocating saw (Miller-Robinson Company).
Compared to loppers and the reciprocating air saw, which
use small amounts of free air and operate at low pressures, cir-
cular air saws require large amounts of air and operate best at
high pressures (100-175 psi).
Fig. 8.-An air-operated lopper.
Fig. 8.-An~ air-operated lopper.
Series of air loppers and reciprocating saws, operated by
large capacity single stage compressors, have been used rather
widely in recent years. These same compressors can be used
for the circular air saws but are not as well adapted as the 2-
stage type. This is because 2-stage compressors are best when
working pressures in excess of 125 psi are required. They are
equipped with 2 cylinders, 1 large, 1 small. The air is first com-
pressed in the large cylinder (low pressure cylinder), then dis-
charged into the small cylinder (high pressure cylinder) through
an intercooler. There, it is compressed to the required pressure.
By separating the stages and cooling the air between the stages,
power requirements are lower and proper lubrication of cylinder
and pistons can be maintained. On the other hand, single stage
compressors have only 1 cylinder, a low pressure one. Single
stage compressors overheat at excessively high pressures.
Air compressed above atmospheric pressure will not hold as
much moisture as free air. Condensation should therefore be
allowed to settle before the air reaches the outlet piping. This
function is performed by the receiver tank. The tank also serves
as an air reservoir; it equalizes the pulsations coming from the
compressor; it collects grease held in suspension by the com-
pressed air as it leaves the compressor; it reduces the friction
of air in the pipe system; and it cools the air before it enters
the transmission system. Water and grease should therefore
be drained from the tank occasionally. A tank capacity of ap-
proximately 10 gallons is satisfactory for average conditions.
It should have an ASME National Board working pressure of 200
pounds. A 200-pound pressure gauge should be attached to
Compressor assemblies for pruning may be engine or PTO-
driven. In either case, they should be equipped with constant
speed control unloaderr), such as that which holds the suction
valves open when the top pressure is reached. This pressure
is pre-adjusted manually by the operator according to the re-
quirements of the pruning tools. The compressor should have
sufficient capacity to unload occasionally under maximum work-
ing conditions. This permits cool air to be alternately drawn
into and discharged from the cylinders and will result in cooler
operation for both compressor and engine.
Most operators purchase the compressor assembly in 1 com-
plete unit. The only specifications necessary in this case are
1. P.T.O. or engine driven.
2. Operating pressure range.
3. Free air delivery.
If P.T.O.-driven, specify whether 540 or 1,000 rpm.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
Florida State University and United States Department of Agriculture, Cooperating
M. O. Watkins, Director