metal work power saw
TRANSCRIPT
Instructor: Mr. Tulloch
Metal Work Engineering
Power Hacksaw
ObjectivesState safety precautions associated with
power sawIdentify the main parts of the sawSet up work and select speeds and feedsPerform cutting operations (square cutting,
angular cutting)
Power SawsPower saw are used to cut stock to the desired
length. It is more accurate than hand saws.
Types of Power SawPower HacksawsBand SawsCircular power saws
Power HacksawPower 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.
Parts of the Power HacksawBaseA mechanism causing the saw frame to
reciprocateClamping ViceFrameTableFeed knobCoolant pump
Types of Power HacksawsDirect Mechanical driveHydraulic drive
Direct Mechanical Drive
Hydraulic Drive
Feed MechanismThe feed mechanism regulates the amount
of downward pressure the blade applies on the material during the forward stroke.
Types of Feed PressureMechanical 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
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.
Operating the SawWhen 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.
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’.
Driving MechanismCircular 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.
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
Types Of BladeWhen 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.
Blade PitchThe correct pitch of teeth is determined by:The size of the section,The material to be cut
Type of PitchCoarse- soft steel, cast iron and bronzeRegular- anneal high carbon steel and high
speed steelMedium- for solid brass stock, iron pipe,
and heavy tubingFine- thin tubing and sheet metals
SafetyNever attempt to mount, measure or remove
work unless machine is turned offGuard long materials at both endsUse cutting fluid whenever possibleHold thin materials flat in the vice to
prevent breaking of blades
Circular Band Saw
Types of Band Saw Machines
Double Column Construction Horizontal Band Saw Machines
Vertical Band Saw MachinesCircular Sawing Machine