3. Objectives
State safety precautions associated with
power saw
Identify the main parts of the saw
Set up work and select speeds and feeds
Perform cutting operations (square cutting,
angular cutting)
4. Power Saws
Power saw are used to cut stock to the desired
length. It is more accurate than hand saws.
5. Types of Power Saw
Power Hacksaws
Band Saws
Circular power saws
6. Power Hacksaw
Power hacksaws are used to cut large sizes
(sections) of metals such as steel. Cutting
diameters of more than 10/15mm is very hard
work with a normal hand held hacksaw. Therefore
power hacksaws have been developed to carry out
the difficult and time consuming work. The power
hacksaws main feature is its reciprocating frame.
The heavy ‘arm’ moves backwards and forwards,
cutting on the backwards stroke with the help of a
downward force.
7. Parts of the Power Hacksaw
Base
A mechanism causing the saw frame to
reciprocate
Clamping Vice
Frame
Table
Feed knob
Coolant pump
8. Types of Power Hacksaws
Direct Mechanical drive
Hydraulic drive
11. Feed Mechanism
The feed mechanism regulates the amount
of downward pressure the blade applies on
the material during the forward stroke.
12. Types of Feed Pressure
Mechanical Feed- light
feed pressure on soft
materials and work with
small cross-section.
Hydraulic Feed- constant
pressure but designed that
when hard spots
encountered, the feed stop
or decrease the pressure
until the hard spot has
been cut through
Gravity Feed-
which provides for
the weights on the
saw frame. These
weights can be
shifted to increase
or decrease the
pressure
13. Operating the Power Hacksaw
The metal to be cut is held in a machine vice
which is an integral part of the base. Turning
the handle tightens or loosens the vice. The
vice is very powerful and locks the metal in
position.
14. Operating the Saw
When cutting is taking place, the metal and especially the
blade heats up quickly. Coolant should be fed onto the
blade, cooling it down and lubricating it as it cuts through
the metal.
Without the use of coolant the blade will over heat and
break/snap. This can be dangerous as the blade can break
with powerful force, shattering.
15. When the metal is placed and fixed in the vice,
the blade is lowered onto its top surface.
The diagram below shows the ‘arm’ being
lowered with the ‘adjusting handle’.
16. Driving Mechanism
Circular motion is transformed into linear
motion. The crank which is the rotating disc,
the slider which slides inside the tube and
the connecting rod which joints the parts
together.
17. Driving Mechanism
If the belt is placed on the smaller pulley wheel the speed of
cut will be fast. Changing the belt so that it runs round the
larger pulley wheel will reduce the speed
18. Types Of Blade
When selecting the
blade at least three
teeth must be in
contact with the
work at all times.
Flexible- used for
cutting odd shapes
and is shatter proff.
All hard- straight
and accurate cutting
but shatter when
breaks.
19. Blade Pitch
The correct pitch of teeth is determined by:
The size of the section,
The material to be cut
20. Type of Pitch
Coarse- soft steel, cast iron and bronze
Regular- anneal high carbon steel and high
speed steel
Medium- for solid brass stock, iron pipe,
and heavy tubing
Fine- thin tubing and sheet metals
21. Safety
Never attempt to mount, measure or remove
work unless machine is turned off
Guard long materials at both ends
Use cutting fluid whenever possible
Hold thin materials flat in the vice to
prevent breaking of blades
