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Chapter. 11. Sawing and Cutoff Machines. Objectives. Identify the various types of sawing and cutoff machines Select the correct machine for the job to be done Mount a blade and prepare the machine for use Position the work for the most efficient cutting
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Chapter 11 Sawing and Cutoff Machines
Objectives • Identify the various types of sawing and cutoff machines • Select the correct machine for the job to be done • Mount a blade and prepare the machine for use • Position the work for the most efficient cutting • Safely operate sawing and cutoff machines
Metal-Cutting Power Saws • Used to cut the stock to required length • Three principal types • Reciprocating-type • Band-type • Circular-type
Metal-Cutting Power Saws (Cont.) Goodheart-Willcox Publisher
Power Hacksaw • Uses reciprocating motion to move blade across work, cuts on the backstroke • Positive feed • Definite pressure feed • Gravity feed • Feed adjusted to meet varying conditions
Power Hacksaw Accessories • Swivel vise • Angular cuts made quickly • Quick-acting vise • Faster manual clamping of the workpiece • Power stock feed, power clamping of work, automatic cycling • Automate the cutting operation • High-speed cutting requires use of a coolant
Selecting a Power Hacksaw Blade • Three-tooth rule • At least three teeth must be in contact with work • Large sections and soft material • Require a coarse-tooth blade • Small or thin work and hard material • Use a fine-tooth blade • Change pressure based on material
Types of Blades • Flexible-back blade • Safety requirements demand a shatterproof blade • Best for cutting odd-shaped work • All-hard blade • Used for majority of cutting jobs • Best for straight, accurate cutting • Made from tungsten and molybdenum steels, tungsten carbide teeth on steel alloy backs • Follow “rule-of-thumb” when selecting blade
Mounting a Power Hacksaw Blade Goodheart-Willcox Publisher Goodheart-Willcox Publisher
Cutting with a Power Hacksaw • Measure off distance to be cut • Allow ample material for facing if necessary • Mark the stock • Mount work firmly on machine • Use stop gage if several sections are to be cut • Apply ample supply of coolant if the machine has a built-in coolant system
Power Band Saw • Horizontal band saw • Referred to as the cutoff machine • Advantages over power hacksaw • Greater precision • Faster speed • Less waste
Selecting a Band Saw Blade • Made with raker teeth or wavy teeth • Tooth pattern determines the efficiency of a blade in various materials • Standard tooth • Skip tooth • Hook tooth Goodheart-Willcox Publisher
Selecting a Band Saw Blade (Cont.) • Consult blade manufacturer’s chart for proper blade to use and blade tension • Blade guides should be adjusted to provide adequate support • Most problems caused by poor machine condition • Follow maintenance program on a regular basis
Problems When Using Power Hacksaws and Band Saws • Blades breaking • When dropped on work • Loose blade or excessive feed • Crooked cutting • Usually result of worn blade • Loose blade or blade rubbing • Excessive blade pressure • Remember to reverse work after replacing blade, cutting on opposite side
Additional Problems • Blade pin holes breaking out • Caused by dirty mounting plates or too much tension on blade • Blade twists and strain, causing pin hole to break out • Premature blade tooth wear • Insufficient or excessive feed pressure • Lack of coolant or poorly adjusted machine
Additional Problems (Cont.) • Teeth strip off • Starting cut on sharp corner • Be sure work is positioned correctlyand clamped securely • Use proper blade for work Goodheart-Willcox Publisher
Metal-Cutting Circular Saws • Found in many areas of metalworking • Primarily production machine • Divided into three classifications • Abrasive cutoff saw • Cold circular saw • Friction saw
Abrasive Cutoff Saw • Cuts material using rapidly revolving, thin abrasive wheel • Most material can be cut to close tolerances • Special heat-resistant abrasive wheels are available • Two classifications • Dry • Wet
Cold Circular Saw • Makes use of a circular, toothed blade • Capable of producing very accurate cuts • Large cold circular saws can sever round metal stock up to 27″ (675 mm) in diameter
Friction Saw • Operates at very high speeds • Actually melts its way through metal • May or may not have teeth • Teeth used to carry oxygen to cutting area • Find many applications in steel mills to cut red-hot billets
Power Saw Safety • Never operate while senses are impaired • Get help when lifting, cutting heavy material • Clean oil, grease, and coolant from work area • Remember burrs on cut pieces are sharp • Follow manufacturer’s instructions for tensioning a blade • Handle blades with extreme care • Mount work solidly before starting cut
Power Saw Safety (Cont.) • Make sure all guards are in place before using • Wear a dust mask and full face shield when necessary • Avoid standing directly in line with blade • Use brush to clean chips from machine • Keep hand out of way of moving parts • Stop machine before making adjustments • Have any injuries, even minor ones, treated immediately