VARIABLES
WHICH AFFECT BANDSAW BLADE LIFE
A practical overview of bandsawing basics
Variable #1
The Operators
Why is the saw operator a variable in bandsaw cutting?
• The operator knows the machine best
• The operator has control over many other variables
Variable #2
Number of Teeth in Band
Too few teeth . . . tooth straddle, which can cause tooth strippage
The 3
Tooth Rule
Too many teeth . . . loads the gullet, which can cause tooth strippage
1 – The tooth cuts a chip
which fills the gullet
2 – When the gullet is full,
pressure is created
3 – When the pressure is not
relieved, the result is a crooked
cut, stripped teeth, or both!
Both tooth conditions can create the same result! . . .
Tooth Selection Guidelines:
Minimum 3 teeth in cut
Optimum 6-12 teeth in cut
Maximum 24 teeth in cut
Variable #3
Tooth Style
Regular
• Rake angle of 0 degrees, full round gullets
• Used for cutoff and contour cutting - general purpose
Skip
• 0 degree rake and shallow gullets
• Good for cutting large sections of soft, non ferrous metals and wood
Hook
• Positive rake angle and deep gullets
• Good for cutting non ferrous metals and hard or soft wood
Intenss PRO
• Large variable pitch teeth, up to 12 degree positive rake angle
• Production cutting, mild to stainless steels
Variable #4
Tooth Set
Regular Raker Set
• One tooth set to the left, one to the right, and a third “raker” tooth, which is 'unset' or straight
• Used for general purpose cutoff and contour cutting
Wavy Set
• Groups of teeth set alternately to the left and right in a wave-like pattern
• Reduces strain of individual teeth
• Used for cutting thin stock on a variety of shapes
Modified Raker Set
• Raker teeth are at regular intervals, with multiple set teeth in between (i.e. L-R-L-R-Raker)
• Used for cutting a wide variety of shapes and sizes
• Allows broader material size variation for varied cutting
• General purpose
Variable #5
Band Tension
How do I know what the proper bandsaw blade tension is?
• Measure it . . . With a Starrett Saw Tension Gage
Recommended Tension
Carbon blades - 15,000 - 20,000 PSI
Bi-Metal blades thru 1 1/2” - 25,000 - 35,000 PSI
Bi-Metal blades 1 1/2” and wider - 30,000 - 40,000 PSI
As a general rule of thumb, the higher end of the tension range should
be used when the guide arms are further apart and the lower end of
the range should be used when the guide arms are closer together.
Variable #6
Blade Speed
 How does blade speed become a variable? The proper
blade speed will affect blade life:
•
•
for tough material, generally slow the blade speed
for softer material, generally increase the blade speed
 How do I calculate my blade speed?
1.
2.
3.
4.
5.
6.
determine the length of the band saw blade
mark a spot on the blade (or locate the weld)
start up the saw
time one rotation of the blade (in seconds)
divide the number of seconds for one rotation into 60 seconds
multiply the result by the length of the blade
* The answer is the Surface Feet Per Minute!
Variable #7
Break-In Procedure
 What is a proper break-in? Reduce the normal feed rate by 1/2
Recommended Band Speed in SFPM:
Square inches to cut for break-in:
Why? This will 'hone' the teeth of
the bandsaw blade and make it last
longer.
Think of your band saw teeth as you
would a freshly-sharpened pencil . . . the
tip is easily broken when you begin to
write. A band saw tooth reacts the same
way. Band speed is not what breaks
down the tooth tip during break-in, the
pressure is.
300
90
250
75
200
60
150
40
100
25
50
10
Band Saw Blade Tooth Tips Magnified
Proper
Break-in
Reduced feed
pressure
‘hones’ the cutting
edge of the tooth
Improper
Break-in
Excessive feed
pressure ‘breaks
down’ the sharp
tooth edge prematurely
Remember . . . Proper break-in for your bandsaw blade will
greatly improve bandsaw blade cutting life.
Be sure to always take a chip!!
Variable #8
Feed Rate
Feed rate is measured in Square Inches per Minute (SIM)
Feed Rate too light
Rubs the tooth dull
Feed Rate too heavy
Premature tooth wear
Recommended Feed Rate
Optimum blade life
How do we determine the proper feed rate?
1. Determine the material that you are cutting
2. Decide which band saw blade to use (carbon, bimetal, carbide)
3. Consult a feed rate chart for the material being cut, and set the
saw’s feed pressure accordingly
Variable #9
Blade Quality
There are vast differences in the way bandsaw blades will perform. Bandsaw quality varies widely,
depending upon the manufacturer and blade type. The type could be any one of the following:
Carbon
Bi-Metal
Carbide Tipped
An example of blade type differences are Red Hardness and Shock Resistance:
The relative Red Hardness of tooth tips
Temperature Tolerance Range of Cutting Edges
Carbide Tipped
Rc
Carbon
M-2
M-30
M-42
Shock resistance in a tooth tip is a tradeoff . . .
. . . Long wear versus low shock resistance
Shock Resistance vs. Wear Resistance
S
h
o
c
k
W
e
a
r
Increase in Rockwell hardness of tooth tip
Carbon
M-2
M-30
M-42
Carbide Tipped
Variable #10
Machine Type
The Machine Type is another variable in bandsaw cutting
Different machine makes and models have different cutting applications
Horsepower ratings can affect the ability to cut some materials
Variable #11
Wheels
Proper adjustment of the wheels can create variable blade
performance. There are typically two wheels on a bandsaw
machine, and they should be checked for proper alignment,
bearing condition, and flange condition.
Idler Wheel
Drive Wheel
Correct Tracking
Idler Wheel Alignment
Improper Tracking, Slippage
Blade Breakage, Flange
Wear
Variable #12
Machine Condition
Machine condition, good and bad, can create a high degree of
variation in bandsaw cutting productivity and accuracy.
Is the machine OLD?
Is the machine NEW?
Has the machine been well maintained?
Variable #13
Proper Vises
Vice Adjustment – Front View
Why vises? . . . To hold
work firmly and accurately.
Band Saw Blade
Saw Bed
Movable
Vice
Vice Adjustment – Top View
Proper alignment of the vice
will allow square cuts . . .
Movable Vice
. . . Improper alignment of
the vice will create crooked
cuts
Machinist’s
Square
Band Saw Blade
Machinist’s
Square
Fixed Vice
Adjust fixed vice to square with band saw blade
Band Saw Squareness – End View
Band saw blade
squareness also affects the
straightness of the cut
Fixed Vice
Machinist’s
Square
Alignment Tool
Band Saw Blade
Variable #14
Guides
Guides should support and align the blade,
when properly adjusted they. . .
maintain a STRAIGHT
versus a
. . . and reduce vibration
cut . . .
Variable #15
Guide Arms
Guide arms should be as close to the work as possible, and
secured firmly
Here’s an example
of how properly
adjusted guide arms
should look . . . snug
to the work piece
Wrong!
Correct!
When the
adjustable guide
arm is this far away
from the work, the
blade can be
damaged . . .
. . .move the adjustable
guide arm in!
Variable #16
Brushes
 Brushes aid in the clearing of chips from the gullet of the blade,
which helps prevent tooth strippage and leaves smoother cut surfaces
Band Saw Brushes
are very
Important!
 The ends of the brush filaments should just touch the bottom of the
deepest gullet
 Brushes should not be set so that the brush filaments constantly
rub the side of the blade
Variable #17
Coolant
Should . . .
Wash chips out of the blade’s gullets
Cool the tooth tips to reduce heat damage
Lubricate the cut to reduce heat caused by cutting friction
Coolant . . . to
Wash
Cool
Lubricate
Variable #18
Material Machinability
The “toughness” of metal can vary tool life.
Materials can look the same, but vary greatly in it's
machinability.
Cold Rolled
Stainless
Inconel
Most materials have a “machinability rating”, with 100% being “free
machining” and anything lower than 100% being more difficult to work
Variable #19
Material Hardness
Material Hardness can affect cutting performance . . . the higher
the hardness of the work piece, the more difficult it is to cut
 an Rc* of 40 has a machinability rating approaching zero
* Rc is an abbreviation for Rockwell 'C' scale, a measurement used to test
the relative hardness of metals
Variable #20
Material Shape
The shape of the work piece can affect cutting performance . . .
 Structural material and small
solids tend to be harder on the
blade
 Work piece positioning on the saw
can affect cutting performance . . .
try to position the material so there is
as little cross section dimensional
variance as possible across the
blade’s path
Multiple “shock” points when
cutting structural materials
Variable #21
Production Requirement
Piece lots?
Short production
runs?
Production cutting –
long runs?
What is the customer’s requirement? Is it pieces on the
floor?
When making a recommendation, consider whether the blade will
face continuous use or intermittent use . . .
Different operating conditions and different expectations will help
determine what type of blade is selected
VARIABLES . . . A REVIEW
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The Operators - The largest single variable.
The Number of Teeth in the Blade - 3 minimum, 6 - 12 optimum, 24 maximum.
Tooth Style - Standard, Skip, Hook, or Variable Pitch.
Tooth Set - Regular, Wavy, Alternate, Raker, or Modified Raker.
Band Tension - Measured with a Starrett Tension Gage.
Band Speed - Start with the manufacturer’s recommendation.
Break-In Procedure - Reduce normal feed rate by 1/2.
Feed Rate - Set rate by square inches per minute suggested by manufacturer.
Band Quality - Carbon vs Bimetal or Carbide Tipped, one brand vs another.
Machine Type - Different makes and models, horsepower of motor.
Wheels - Check alignment, bearings, flanges.
Machine Condition - Old, new, well-maintained.
Proper Vises - To hold the work firmly.
Guides - Should support the band, roller guides should be adjusted properly.
Guide Arms - Should be as close to the work as possible for support.
Brushes - Aid in the clearing of chips from the gullet of the band.
Coolant - Should wash, cool and lubricate.
Material Machinability - The toughness of a metal can reduce tool life.
Material Hardness - A Rc of 40 has a machinability approaching 0.
Material Shape - Structurals and small solids tend to be harder on the blade.
Production Requirement - Continuous vs intermittent use.
Any one variable or any combination of the above variables can affect blade life!