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Types of Metal Saws
Session 4
Shop Tools and Techniques 2
Cutting Off Materials
• Five most common methods of cutting off material• Hacksawing• Bandsawing• Abrasive cutting• Cold sawing• Friction sawing
Shop Tools and Techniques 3
Power Hacksaw
• Reciprocating type of saw• Frame and blade travel back and forth• Pressure applied automatically on forward
stroke
• Limited use in machine shop work
• Usually permanently mounted to floor
Shop Tools and Techniques 4
Power Hacksaw
Shop Tools and Techniques 5
Power Hacksaw
Shop Tools and Techniques 6
Horizontal Bandsaw
• Flexible, belt like "endless", blade that cuts continuously in one direction
• Thin, continuous blade travels over rims of two pulley wheels and passes through roller guide brackets• Support blade and keep it running true
• Popular for high production and versatility
Shop Tools and Techniques 7
Horizontal Bandsaw
Shop Tools and Techniques 8
Abrasive Cutoff Saw
• Cuts by means of thin, abrasive wheel revolving at high speed
• Well suited for cutting most metals and materials such as glass and ceramics
• Can cut to close tolerances• Can be performed under dry conditions
• Use of cutting fluid keeps work and saw cooler and produces better surface finish
Shop Tools and Techniques 9
Abrasive Cutoff Saw
Shop Tools and Techniques 10
Cold Circular Cutoff Saw• Uses circular blade similar to one
used on wood-cutting table saw
• Generally made of chrome-vanadium steel
• Suited for cutting aluminum, brass, copper, machine steel, and stainless steel
Shop Tools and Techniques 11
Cold Circular Cutoff Saw
Shop Tools and Techniques 12
Friction Sawing
• Burning process by which saw band (with or without) saw teeth, is run at high speeds to burn or melt its way through metal• 10,000 to 25,000 sf/min
• Cannot be used on solid metal• Amount of heat generated
• Excellent for cutting structural and honeycombed parts of machine or stainless steel
Shop Tools and Techniques 13
Horizontal Bandsaw Parts• Frame - hinged at motor end with two
pulley wheels over which continuous blade passes
• Step Pulleys - Used to vary blade speed
• Roller guide brackets - Provides rigidity for section of blade
• Blade tension handle - Used to adjust tension on saw blade
• Vise - Mounted on table, holds work
Shop Tools and Techniques 14
Saw Blades
• Commonly made of high-speed tungsten and high-speed molybdenum steel• Hardened completely for power hacksaw• Flexible blades on bandsaws have teeth
hardened
Shop Tools and Techniques 15
Saw Blades
• Manufactured in various degrees of coarseness, ranging from 4-14 pitch• 10-pitch blade used for general-purpose
sawing• Always select saw blade as coarse as
possible• Always have two teeth of blade in contact
with work at all times
Shop Tools and Techniques 16
Installing a Blade
• Make sure teeth are pointing in direction of saw travel or toward motor end of machine
• Adjust blade tension to prevent blade from twisting or wandering during cut
• Rotate work ½ turn in vise, if need to replace blade before cut finished• Prevent new blade from jamming
Shop Tools and Techniques 17
Sawing
• Important that correct type and pitch of saw blade be selected and run at proper speed
• Blades• Finer tooth when cutting thin cross sections
and extra-hard materials• Coarser tooth used for thick cross sections
and soft, stringy material• Speed
• Should suit type and thickness of material• Too fast will dull saw teeth quickly
Shop Tools and Techniques 18
Advantages of the Vertical Bandsaw
Shop Tools and Techniques 19
Advantages of the Vertical Bandsaw
Shop Tools and Techniques 20
Advantages of the Vertical Bandsaw
Shop Tools and Techniques 21
Contour Bandsaw Parts
• Fabricated from steel
• Basic parts• Base• Column• Head
Shop Tools and Techniques 22
Bandsaw Applications
• Notching• Sections of metal
removed in one piece
• Slotting• Quick and accurate
without expensive
fixtures
Shop Tools and Techniques 23
• Three-dimensional shaping
• Radius cutting• Internal or external contours• Internal sections removed
in one piece
Bandsaw Applications
Shop Tools and Techniques 24
Bandsaw Applications
• Splitting• Accomplished quickly with
minimum waste
• Angular cutting• Work clamped at any angle• Table may be tilted
Shop Tools and Techniques 25
Bandsaw Blade Types
• Three kinds of blades commonly used• Carbon-alloy• High-speed steel• Tungsten-carbide tipped
• For best results, must consider• Kind of saw-blade material and tooth form• Pitch set• Width• Gage needed
Shop Tools and Techniques 26
Tooth Forms
• Precision (regular)• Most generally used• 0º rake angle, 30º back clearance• Used for fine finish
Shop Tools and Techniques 27
Tooth Forms• Claw (hook)
• Positive rake on cutting face• Faster cutting, longer lasting
than buttress
Shop Tools and Techniques 28
Tooth Forms
• Buttress (skip)• Teeth spaced farther apart• Tooth angles same as
precision teeth• Used on thick work sections
Shop Tools and Techniques 29
Pitch
• Numbers of teeth per standard reference length• Inch standard = No. teeth/inch• Metric standard = No. teeth/25 mm
• Thickness of material to be cut determines pitch of blade to use• Coarse: thick, Fine: thin
• Two teeth in contact with work at all times
Shop Tools and Techniques 30
Set
• Amount teeth offset either side of center to produce clearance for back of band• Wave set
• Group of teeth offset to right and next to left• Structural steel or pipe
• Straight set• One tooth offset to right
and next to left• Light nonferrous castings
• Raker set• One tooth offset to right, one to left,
and third tooth straight
Shop Tools and Techniques 31
Width
• Wide blade used for straight, accurate cuts
• Narrow blades used to cut small radii
• Radius charts show proper width of blade are found on all bandsaws• Choose widest blade that can cut smallest
radius
Shop Tools and Techniques 32
Gage
• Thickness of saw blade
• Thick blades stronger than thin blades
• Thickest blade possible should be used for sawing tough material
• Standardized according to blade width
½ in wide are .025 in. thick5/8 in. and ¾ in. wide are .032 in. thick1 in. wide are .035 in. thick
Shop Tools and Techniques 33
Calculate Lengthof Saw Blade• Packaged in coils 100 to
150 ft. in length• Cut length required and
weld ends• Twice center distance
between each pulley and add it it one pulley's circumference
Blade length = 2 (CD) + µ D
Shop Tools and Techniques 34
Sawing Internal Sections
• Starting hole must be drilled through section to be removed to allow saw blade inserted and welded
• Good practice to drill hole at every point where sharp turn must be made to allow workpiece to be turned easily
Shop Tools and Techniques 35
Butt Welder
• Permits convenient welding of blade for removal of internal sections
• Blades cut from coil stock and welded into continuous band• Broken blades may be welded and used• Resistance-type welders fuse ends of
blade• Butted ends of welded blade must not
overlap in width, set or pitch of teeth
Shop Tools and Techniques 36
Trimming and Blanking Dies• Possible to use internal cutting
technique to make short-run trimmings and blanking dies
• Internal section (slug) becomes punch and external material forms the die
• Table must be tilted to provide proper clearance for die
Shop Tools and Techniques 37
Friction Sawing
• Fastest means of sawing ferrous metals up to 1 in. in thickness
• Saw traveling at hi-velocity (15,000 sfm)
• Tremendous heat generated by friction brings metal immediately ahead of saw teeth to plastic state and teeth easily remove metal• Blade remains cool (time to cool as it travels)
Shop Tools and Techniques 38
Friction Sawing
• Used on hardened ferrous alloys, armor plate, stainless-steel alloys• Cannot cut aluminum, brass, plastics -
materials weld to blade and clog teeth
• Machines resemble vertical band machine but of heavier construction
• Bands made of standard carbon-alloy steel but thicker
• Widths of .250, .750 and 1 in (10, 14 pitch)
Shop Tools and Techniques 39
Friction Sawing
• Saw band almost completely covered to protect operator from sparks
Shop Tools and Techniques 40
High-Speed Sawing
• Performed at speeds ranging from 2000 to 6000 sfm
• Used on nonferrous metals and wood, plastic and rubber
• Same machine setups and procedures apply as for conventional sawing
• Chips must be removed rapidly• Buttress of claw-tooth blades most efficient
Shop Tools and Techniques 41
Band Filing
• Better finish than conventional sawing
• Band file• Steel band of short,
interlocking file segments• Forms continuous loop• Obtained in flat, oval, and
half-round cross sections; bastard and medium cuts;and in widths of .250, .375, and .500 in.
Shop Tools and Techniques 42
Knife-Edge Blades
• Available with knife, wavy, and scalloped-edge blades
• Special roller guides must be used• Used for cutting soft,
fibrous materials• Scalloped-edge blades
suited for cutting thincorrugated aluminum
Shop Tools and Techniques 43
Spiral-Edge Blades
• Round blade has continuous helical cutting edge around the circumference
• Provides a cutting edge of 360º• Permits machining of intricate contours
and patterns Require special guides• Two types: spring-tempered and all-
hard
Shop Tools and Techniques 44
Line-Grinding Bands
• Have abrasive bonded to thin edge of steel band• Aluminum oxide or silicon carbide
• Used to cut hardened steel alloys and other materials which could not be cut by bandsawing
• Requires high speed (3000 to 5000 sfm)• Requires coolant
Shop Tools and Techniques 45
Diamond-Edge Blades
• Used to cut superhard space-age materials as well as ceramics, glass, silicon, and granite
• Has diamond particles fused to edges of saw teeth
• Generally requirecoolant
• Very expensive
Shop Tools and Techniques 46
Polishing Bands
• Used to remove burrs and provide good finish to filed or sawed surfaces
• Continuous loop of 1-in-wide abrasive cloth manufactured to specific machine length
• Available in several grain sizes• Aluminum-oxide and silicon-carbide abrasive
• Mounted in same manner as saw band
Shop Tools and Techniques 47
Electro-Band Machining
• Used to machine materials such as thin-wall tubing, stainless steel, aluminum and titanium honeycombing
• Low-voltage, high-amperage current fed into saw blade• Workpiece connected to opposite pole of circuit
• Work comes close to band; continuous electric spark passes from knife edge to work
• Arc disintegrates work• Blade does not touch workpiece
• Coolant used to prevent damage to work
Shop Tools and Techniques 48
Electro-Band Machining
Shop Tools and Techniques 49
Bandsaw Attachments: Work-Holding Jaw
• Device used by operator to hold and guide work into saw
• Connected toweight-typepower feed sooperator merelysteers work
Start Hole
Shop Tools and Techniques 50
Other Band Attachments• Disk-cutting attachment
• Permits cutting of accurate circles from approximately 2.5 to 30 in. in diameter
• Cutoff and mitering attachment• Used to support work when square or
angular cuts are made
• Ripping fence• Provides means for cutting long sections of
flat bar stock or plate into narrow parallel sections