SAFETY PRECAUTIONS WHEN WORKING WITH POWER SAWS M t k l h th i t d di • Mount or remove work only when the saw is stopped and is raised well above the vise. • Clamp the w/p securely on both sides of the blade if possible • Clamp the w/p securely on both sides of the blade if possible. • Use only blades that are in good condition and which are the correct kind for the material being cut correct kind for the material being cut. • Operate the machine at a cutting speed and feed rate that does not strain the machine or the blade. • Keep hands away from the saw blade when it is running. • Stand out of line with the blade when starting an abrasive cutoff saw. D tb d i f t f h k f h th M E T D E P A R T M E N T M E C H A N I C A L E N G I N E E R I N G T E C H N O L O G Y 1 • Do not bend over in front of a power hacksaw frame when the m/c is running.
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May 14, 2015
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SAFETY PRECAUTIONS WHEN WORKING WITH POWER SAWS
M t k l h th i t d d i• Mount or remove work only when the saw is stopped and is raised well above the vise.
• Clamp the w/p securely on both sides of the blade if possible• Clamp the w/p securely on both sides of the blade if possible.
• Use only blades that are in good condition and which are the correct kind for the material being cutcorrect kind for the material being cut.
• Operate the machine at a cutting speed and feed rate that does not strain the machine or the blade.
• Keep hands away from the saw blade when it is running.
• Stand out of line with the blade when starting an abrasive cutoff saw.
D t b d i f t f h k f h thMET
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• Do not bend over in front of a power hacksaw frame when the m/c is running.
SAWING MACHINE TYPESSAWING MACHINE TYPES
Classification :
1. Reciprocating : Power hacksaws
2. Circular saw: Cold saw & abrasive
3. Band saw: Horizontal, vertical cutoff
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Reciprocating Sawing Machines: Hacksaws :# Used primarily for cutting to length metal of various sizes & shapes.# Used primarily for cutting to length metal of various sizes & shapes.
# These sawing m/c vary in design from light-duty to heavy-duty m/c.g y g g y y y
# Actual cutting takes place in only one direction and the saw blade is lifted slightly on the return stroke.
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3 Fig. Reciprocating power hacksaw
Circular Sawing Machines :
Commonly known as cold sawing machines.
Work pieces are clamped in a vise or fixture, one or more pieces at aWork pieces are clamped in a vise or fixture, one or more pieces at a time. The circular blade is mounted on a power driven arbor & rotated through the cut.
are also used for cutting off stock.Abrasive discsAn abrasive disc is a thin, flexible grinding wheel.The disc is mounted on a machine that can be adapted for either wet or dry cutting.
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Horizontal Band saws :
Are available in a wide variety of types and sizes.
It has a flexible, "endless" blade which cuts continuously in one di ti Th thi bl d t l th i f t lldirection. The thin blade travels over the rims of two pulley.
, hinged at the motor end, has two pulley wheels over The saw framewhich the continuous blade passeswhich the continuous blade passes.
are used to vary the speed of the continuous blade.step pulleysThe
brackets provide rigidity for a section of the blade roller guideThe and prevent it from wandering and twisting.
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is used to adjust the tension on the blade tension handleThe saw blade.
mounted on the table can be adjusted to hold various viseThe sizes of w/p.sizes of w/p.
BLADE TENSION
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6 Fig. The main parts of horizontal Bandsaw
Sawing Hints :# Never attempt to mount, measure or remove work unless the saw
is stopped.
# Guard long material at both ends to prevent anyone from coming i t t ith itin contact with it.
# Use cutting fluid, whenever possible, to help prolong the life of the saw blade and improve the cutting actionthe saw blade and improve the cutting action.
# When sawing thin pieces, hold the material flat on the vise to prevent the saw teeth from breakingprevent the saw teeth from breaking.
# Use caution when applying extra pressure to the saw frame as this generally causes work to be cut out of square.g y q
# When several pieces of the same length are required, set the stop gauge saws.
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CONTOUR BANDSAW PARTS AND ACCESSORIESACCESSORIES
The contour bandsaw is generally fabricated from steel.g y
The contour bandsaws has many advantages in the metal-cutting trade.
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9Contour bandsaw parts
Contour Bandsaw Parts and Operations
The basic parts are (1) base (2) column (3) head
Base :Base : The base of the contour bandsaw supports the column and houses the assembly that provides the drive for the blade.
Column :
The column supports the head, the left-hand blade guard, welding it d th i bl d h d h lunit, and the variable-speed handwheel
Head :
The parts found in the head of a saw are generally used to guide or support the saw band.
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Bandsaw Operations
(a) Notching : Sections of metal removedin one piece
(b) Slotting : Quick and accurate without i fi texpensive fixtures
Work clamped at any : Angular cutting(c)
angle & table may be tilted
(d) Radius cutting : Internal or external contours
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Horizontal Bandsaw Blades
High speed tungsten and high speed molybdenum steel.
CONTOUR BAND SAW BLADES
Three types of saw blades generally used are
(1) Carbon alloy(1) Carbon-alloy,(2) High-speed steel, (3) Carbide-tipped blades.
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Tooth Forms
Three types of tooth forms:
This is the most generallyPrecision or Regular Tooth(a) This is the most generally -Precision or Regular Tooth(a). used . It is used when a fine finish and an accurate cut are required.
This tooth form is similar to the -Buttress or Skip Tooth(b). precision tooth; however, the teeth are spaced farther apart Used on thick work sections and on deep cuts in soft materialUsed on thick work sections and on deep cuts in soft material.
–Claw or Hook Tooth(c). It has the same general application as the buttress-tooth formIt has the same general application as the buttress tooth form. It is faster cutting and longer lasting than the buttress tooth, but will not produce smooth finish.
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PITCHNumbers of teeth per standard reference length
Inch standard = No. teeth/inchInch standard No. teeth/inchMetric standard = No. teeth/25 mm
Thickness of material to be cut determines pitch of blade to usepitch of blade to use.Coarse: thick, Fine: thin
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There are three common set patternsW)1( : Wavy)1(
– Alternate arrangement of several teeth to right d l ftand left.
– Used to cut tubes & light sheet metal.
One tooth left & the other right. :Straight) 2(Used for brass, copper & plastic
:Raker) 3(– Three teeth in sequence left, right, & straight.– Used for steel & cast iron
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Blade LengthBlade Length
2* CD+3.14*D
CD= CENTER DISTANCE
D= DIA OF PULLEY
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