Metal-Cutting Saws 1

35-2 Metal-Cutting Saws First crude saw closely followed origin of stone ax and knife Sharp edges of stones were serrated or toothed Cut by scraping away particles of object Great improvement followed the appearance of copper, bronze, and ferrous metals Today steel available for saw blades 2

Types of Metal Saws

35-4 Objectives Name five types of cutting-off machines and state the advantage of each Select the proper blade to use for cutting various cross sections Install a saw band on a horizontal bandsaw Use a bandsaw to cut off work to an accurate length

Methods of Cutting Off Material 35-5 Methods of Cutting Off Material Five most common methods of cutting off material Hacksawing Bandsawing Abrasive cutting Cold sawing Friction sawing 5

Power Hacksaw Reciprocating type of saw 35-6 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 6

35-7 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 7

35-8 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 8

Cold Circular Cutoff Saw 35-9 Cold Circular Cutoff Saw Uses circular blade similar to one used on wood-cutting table saw Generally made of chrome-vanadium steel Carbide-tipped blades used for some applications Suited for cutting aluminum, brass, copper, machine steel, and stainless steel 9

35-10 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 10

35-11 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 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 11

35-12 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 12

Contour Bandsaw Parts and Accessories

36-14 Objectives Name the main operative parts of a contour-cutting bandsaw and state the purpose of each Select the proper tooth form and set for any cutting application Calculate the length of a saw band for a two-pulley machine

Vertical Bandsaw Latest machine tool to be developed 36-15 Vertical Bandsaw Latest machine tool to be developed Early 1930s Widely accepted by industry Fast and economical method of cutting metal and other materials Continuous cutting action on workpiece 15

Advantages of the Vertical Bandsaw 36-16 Advantages of the Vertical Bandsaw 16

Advantages of the Vertical Bandsaw 36-17 Advantages of the Vertical Bandsaw 17

Advantages of the Vertical Bandsaw 36-18 Advantages of the Vertical Bandsaw 18

Contour Bandsaw Parts Fabricated from steel Basic parts Base Column 36-19 Contour Bandsaw Parts Fabricated from steel Basic parts Base Column Head 19

Bandsaw Common Applications 36-20 Bandsaw Common Applications Notching Sections of metal removed in one piece Slotting Quick and accurate without expensive fixtures 20

Bandsaw Common Applications 36-21 Bandsaw Common Applications Three-dimensional shaping Simply follow layout lines Radius cutting Internal or external contours Internal sections removed in one piece 21

Bandsaw Common Applications 36-22 Bandsaw Common Applications Splitting Accomplished quickly with minimum waste Angular cutting Work clamped at any angle Table may be tilted 22

Coolants Power-feed models have cooling system Mist coolant system 36-23 Coolants Power-feed models have cooling system Circulates and discharges coolant against faces of blade and work Mist coolant system Uses air to atomize coolant and direct it (efficient) Recommended for high-speed machining of nonferrous metals Grease-type lubricants and coolants may be applied directly to blade on machines with no system

Power Feed Work and table fed toward blade by hydraulic system 36-24 Power Feed Work and table fed toward blade by hydraulic system Fixed-table machines use gravity to provide steady mechanical feeding pressure Allows operator to use both hands to guide Work forced into blade by cables, pulleys, and weights Force Varied up to about 80 lb. (regular 30-40 lbs) 24

Tooth Forms Precision (regular) Claw (hook) Buttress (skip) 36-25 Tooth Forms Precision (regular) Most generally used 0º rake angle, 30º back clearance Used for fine finish Claw (hook) Positive rake on cutting face Faster cutting, longer lasting than buttress Buttress (skip) Teeth spaced farther apart Tooth angles same as precision teeth Used on thick work sections 25

Pitch Numbers of teeth per standard reference length 36-26 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 26

36-27 Set Amount teeth offset on 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 27

Width Wide blade used for straight, accurate cuts 36-28 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 28

Gage Thickness of saw blade Thick blades stronger than thin blades 36-29 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. thick 5/8 in. and ¾ in. wide are .032 in. thick 1 in. wide are .035 in. thick 29

36-30 Job Requirements Bandsaw operator should be familiar with various types of blades Select one that will do job to specified finish and accuracy at lowest cost Table 36.1 in text provides guide 30

Calculate Length of Saw Blade 36-31 Calculate Length of Saw Blade CD 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 D Blade length = 2 (CD) + µ D 31