2. Sawing and Cutoff Machines
Chapter 11
Sawing and Cutoff Machines

3. 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

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

5. Metal-Cutting Power Saws (Cont.)
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6. 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

7. 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

8. 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

9. 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

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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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