Sawing and Cutoff Machines 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 All-hard 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 Advantages over power hacksaw 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 correctly and 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