1. MACH 112: Cutting Tools & Measurement
Operating Cutoff Saws
MACH 112: Cutting Tools & Measurement

2. Introduction USING CUTOFF MACHINES
The reciprocating saw and the horizontal endless band saw are the most common cutoff machines you will encounter.
Their primary function is to cut long lengths of material into lengths suitable for other machining operations on other machine tools.
The cutoff machine is often the first step in machining a part to its final shape and size.

3. OBJECTIVES Objectives… Use saw blade terminology.
Describe the conditions that define blade selection.
Identify the major parts of the horizontal band cutoff machine.
Properly install blades on horizontal band machines.
Properly use horizontal band machines in cutoff applications.

4. Cutting Speeds USING CUTOFF MACHINES
Many years of machining experience have shown that tool materials cut most effectively if passed through workpiece materials at optimum speeds.
If a tool material passes through the work too quickly, heat of friction can dull the tool or cause it to fail.
Too slow a passage of the tool through a material can result in premature dulling and low productivity.
Cutting speed refers to the amount of workpiece material passing a cutting tool in a given time.
Cutting speeds are measured in feet per minute (fpm).

5. Cutting Speeds USING CUTOFF MACHINES
The shape of the workpiece does not affect the fpm.
Circumference of a round part passing a tool is in fpm.
In sawing, fpm is the speed of each saw tooth as it passes through a given length of material in one minute.
Cutting speeds are a critical factor in tool life.
Productivity will be low if dull or damaged blades must be replaced frequently.
Cost of replacement cutting tools must be considered.

6. Saw Blades - Terminology
USING CUTOFF MACHINES
Saw Blades - Terminology
Blade Kerf - width of the cut produced by the blade.
Blade Width - distance from the tip of the tooth to the back of the blade.
Blade Gage - thickness behind the set of the blade.
Blade Pitch - is the number of teeth per inch.
Fig. G-39 Gage, pitch & width.
Fig. G-38 Kerf.

7. Saw Teeth - Terminology
USING CUTOFF MACHINES
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Saw Teeth - Terminology
Fig. G-40 Saw tooth terminology.

8. Saw Teeth - Terminology
USING CUTOFF MACHINES
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Saw Teeth - Terminology
Tooth Form - the shape of the saw tooth.
Standard, skip, hook.
Fig. G-41 Tooth forms.

9. Saw Teeth - Terminology
USING CUTOFF MACHINES
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Saw Teeth - Terminology
Set - offset of the teeth of a saw blade on each side to provide clearance for the back of the blade both sides of the blade.
Raker and wave are most common.
Raker set is used in general sawing.
Wave is useful when cross-sectional shape of the workpiece varies.

10. Operating the Reciprocating Cutoff Machine
USING CUTOFF MACHINES
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Operating the Reciprocating Cutoff Machine
The reciprocating cutoff machine is known as the power hacksaw, an outgrowth of the hand hacksaw.
The machine consists of a frame-supported blade operated in a back & forth motion.
Power hacksaws may be hydraulically driven or by a crankshaft mechanism.
Fig. G-44 Reciprocating cutoff saw.

11. Making the Cut USING CUTOFF MACHINES tab
Select appropriate speed rate for material being cut.
Secure the workpiece properly.
If cutting material with a sharp corner, begin on a flat side.
Angular material presents a sharp corner to the blade.
Start the saw gently until a small flat is established.
Apply the proper feed.
Fig. G-46 Cutting workpieces with sharp corners.

12. Making the Cut USING CUTOFF MACHINES
If you replace the blade after starting a cut, turn the workpiece over and begin a new cut.
After a new blade has been used a short time, recheck the tension & adjust if necessary.

13. Operating the Horizontal Band Cutoff Machine
USING CUTOFF MACHINES
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Operating the Horizontal Band Cutoff Machine
The horizontal band cutoff machine uses an endless steel band blade with teeth on one edge.
The blade passes through the work continuously, with no wasted motion, and efficiency greater than with a reciprocating saw.
Fig. G-48 Horizontal endless band cutoff machine (Asnuntuck Community College).

14. Operating the Horizontal Band Cutoff Machine
USING CUTOFF MACHINES
Operating the Horizontal Band Cutoff Machine
Kerf of the band blade is narrow as compared with that of the reciprocating hacksaw or abrasive saw.
Minimum amounts of material are wasted in sawing.
Horizontal band saw size is determined by the largest piece of square material that can be cut.
Fig. G-49 Comparison of kerf widths from band, reciprocating, and abrasive cutoff machines (Courtesy of DoALL Company).

15. Operating the Horizontal Band Cutoff Machine
USING CUTOFF MACHINES
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Operating the Horizontal Band Cutoff Machine
Stock is fed by gravity of the saw head.
Feed rate can be regulated by adjusting the spring tension on the saw head.
Some use a hydraulic cylinder to regulate the feed rate.
Cutting fluid is pumped from a reservoir and flows on the blade at the forward guide.
Additional fluid flows on the blade at the point of the cut.
Chips can be cleared from the blade by a rotary brush that operates as the blade is running.

16. Work Holding on the Horizontal Band Saw
USING CUTOFF MACHINES
Work Holding on the Horizontal Band Saw
The vise is the most common work-holding fixture
Rapid-adjusting vises have large capacity and are quickly adjusted to the workpiece.
The vise may be swiveled for miter or angle cuts.
Fig. G-58 Quick-setting vise on the horizontal band saw (Courtesy of DoALL Company).
Fig. G-59 Band saw vise swiveled for angle cutting (Courtesy of DoALL Company).

17. Work Holding on the Horizontal Band Saw
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Work Holding on the Horizontal Band Saw
On some horizontal band cutoff machines, the entire saw frame swivels for making angle cuts.
Stock may be held/nested in a special vise/nesting fixture.
Fig. G-60 Horizontal cutoff saw frame swiveled for angle cuts (Courtesy of DoALL Company).
Fig. G-61 Nesting fixture for sawing multiple workpieces.

18. Installing Blades on the Horizontal Band Machine
USING CUTOFF MACHINES
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Installing Blades on the Horizontal Band Machine
Blades may be ordered prewelded in the proper length for the machine, or obtained in rolls, cut & welded at the sawing machine location.
Be sure teeth are pointed in the direction of the cut.
Ensure the blade tracks properly on the idler & drive wheels.
Fig. G-62 Make sure the blade is tracking properly on the band wheel. (DoALL Company).

19. Installing Blades on the Horizontal Band Machine
USING CUTOFF MACHINES
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Installing Blades on the Horizontal Band Machine
Adjust blade tension using the tension gage or manual tension indicator built into the saw.
Fig. G-64 Band tension indicator attached to the machine.
Fig. G-63 Dial band tension indicator gage (Courtesy of DoALL Company).

20. Making the Cut USING CUTOFF MACHINES tab
Set the proper speed, adjust blade guides and set feed to produce a good chip.
Release the head and lower it by hand until the blade starts to cut.
When the cut is completed, the machine will shut off automatically.

21. Sawing Problems on the Horizontal Band Machine
USING CUTOFF MACHINES
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Sawing Problems on the Horizontal Band Machine
When using a stock stop for sawing duplicate pieces, swing the stop clear of the work after tightening the vise.
A cutoff workpiece can bind between the stop and blade, which will destroy the blade set.
Fig. G-68
Band saw blade with the set worn on one side.

22. Sawing Problems on the Horizontal Band Machine
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Sawing Problems on the Horizontal Band Machine
Improper feeds, band speeds & types of materials being sawed can strip teeth from the band.
Cutting oils/fluids during band sawing will provide smoother, cooler, and faster cutting.
Also flush chips from the kerf.

23. Sawing Problems on the Horizontal Band Machine
USING CUTOFF MACHINES
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Sawing Problems on the Horizontal Band Machine
A blade with a tooth set worn on one side will drift in the direction of the side with a set still remaining, a principal cause of band breakage.
As the saw progresses through the cut the side drift of the blade will place the machine under great stress.
Fig. G-69 Using a band with the set worn on one side will cause the cut to drift toward the side of the blade with the setting remaining.

24. Sawing Problems on the Horizontal Band Machine
USING CUTOFF MACHINES
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Sawing Problems on the Horizontal Band Machine
Thin, parallel workpieces can be cut by using a sharp blade in a rigid and accurate sawing machine.
Chip removal is important to accurate cutting.
Fig. G-71 Thin, parallel cuts may be made with a sharp blade and rigid sawing machine.

25. Review Questions Define blade kerf. Define blade width.
Define blade set.
Define blade gauge.
Name 3 different saw tooth forms.
Name 3 different saw blade sets.
Of the 3 major classes of cutoff saws, which makes the smallest kerf when sawing?
What is one result of a worn tooth set?