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Metal-Cutting Power Saws: Types, Blades, and Safety Procedures

This chapter covers the various types of metal-cutting power saws, including reciprocating, band, and circular saws. It provides information on selecting the right blade, mounting the blade, and conducting efficient cutting. Safety procedures and common problems are also addressed.

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Metal-Cutting Power Saws: Types, Blades, and Safety Procedures

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  1. Chapter 11 Sawing and Cutoff Machines

  2. 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

  3. Metal-Cutting Power Saws • Used to cut the stock to required length • Three principal types • Reciprocating-type • Band-type • Circular-type

  4. Metal-Cutting Power Saws (Cont.) Goodheart-Willcox Publisher

  5. 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

  6. 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

  7. 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

  8. 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

  9. Mounting a Power Hacksaw Blade Goodheart-Willcox Publisher Goodheart-Willcox Publisher

  10. 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

  11. Power Band Saw • Horizontal band saw • Referred to as the cutoff machine • Advantages over power hacksaw • Greater precision • Faster speed • Less waste

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

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