Types of Metal Saws Session 4. Shop Tools and Techniques2 Cutting Off Materials Five most common methods of cutting off material Hacksawing Bandsawing

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


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


Power Hacksaw


Power Hacksaw


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


Horizontal Bandsaw


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


Abrasive Cutoff Saw


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


Cold Circular Cutoff Saw


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


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


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


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


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


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


Advantages of the Vertical Bandsaw






Contour Bandsaw Parts

• Fabricated from steel

• Basic parts• Base• Column• Head


Bandsaw Applications

• Notching• Sections of metal

removed in one piece

• Slotting• Quick and accurate

without expensive

fixtures


• Three-dimensional shaping

• Radius cutting• Internal or external contours• Internal sections removed

in one piece




• Splitting• Accomplished quickly with

minimum waste

• Angular cutting• Work clamped at any angle• Table may be tilted


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


Tooth Forms

• Precision (regular)• Most generally used• 0º rake angle, 30º back clearance• Used for fine finish


Tooth Forms• Claw (hook)

• Positive rake on cutting face• Faster cutting, longer lasting

than buttress


Tooth Forms

• Buttress (skip)• Teeth spaced farther apart• Tooth angles same as

precision teeth• Used on thick work sections


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


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


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


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


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


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


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


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


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)


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)


Friction Sawing

• Saw band almost completely covered to protect operator from sparks


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


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.


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


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


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


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


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


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


Electro-Band Machining


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


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

Documents

Types of Metal Saws Session 4. Shop Tools and Techniques2 Cutting Off Materials Five most common methods of cutting off material Hacksawing Bandsawing