22 Variables Influencing Cutting Tool Life A practical overview of band sawing basics 3 Tool Destroyers • Heat
• Shock
• Abrasion Variable #1 The Operators
Why is the saw operator a variable in band saw 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 stripping
Too many teeth… loads the gullet, which can cause tooth stripping
1 –The tooth cuts a chip 2 – When the gullet is 3 – When the pressure is not which fills the gullet full, pressure is relieved the result is a created crooked cut, stripped teeth, or both!
Tooth Selection Guidelines:
Minimum 3 teeth in cut Optimum 612 teeth in cut Maximum 24 teeth in cut Variable #3 Tooth Style
Raker style tooth Rake angle of 0 degrees Used for cutoff and contour cutting – general purpose
Skip style tooth Same as standard tooth with every other tooth removed Increased gullet capacity Good for cutting nonferrous metals, soft materials, wood, plywood, and plastics
Hook style tooth Similar to skip tooth, but the face of the cutting edge has a 10 degree hook Prevents soft gummy materials from sticking in the gullets Recommended for the same materials as skip tooth, where faster cutting rates are desired Also used for production sawing of large cross‐sections, where ample power is available for a heavy chip load
Variable Pitch style tooth Tooth design that combines more than one tooth pitch to reduce the chatter and vibration Allows broader material size variation for varied cutting applications 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 Variable #5 Band Tension
How do I know what the proper band saw blade tension is? Measure it with a tension meter
Most Saws operate best with the saw blade tensioned to a minimum of 25,000 p.s.i. and a maximum of 32,000 p.s.i. Variable #6 Band Speed • How does band speed become a variable? The proper band speed will affect blade life: – For tough material, generally slow the blade speed – For softer material, generally increase the blade • How do I calculate my band speed? – Determine the length of the band saw blade – Mark a spot on the blade (or locate the weld) – Start 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. X Variable #7 Break‐In/Run‐in Procedure
Q: What is proper break‐in? A: Reduce the normal feed rate by ½
Recommended band speed in SFPM: 300 250 200 150 100 50 Meters per minute (MPM) 90 75 60 45 30 15 Break‐in Sq. inches (SFPM/4) 75 63 50 40 25 10 Break‐in Cm22/Min (meters/min * 6) 540 450 360 275 180 90
Why? This will “hone” the teeth of the band saw 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 breakin, the pressure is. Variable #8 Feed Rate
Feed Rate is measured in Square Inches Per Minute (SIPM) or Meters Per Minute (MPM)
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 Band Quality
There are vast differences in the way band saw blades will perform. Band saw quality varies widely, depending upon the manufacturer and blade type. The type could be any one of the following:
Carbon High Speed Carbide Tipped
An example of band type differences are Red Hardness and Shock Resistance: The relative Red Hardness of tooth tips Temperature Tolerance Range of Cutting Edges
Shock resistance in a tooth tip is a tradeoff… … Long wear versus low shock resistance Variable #10 Machine Type
The Machine Type is another variable in band saw cutting
Different machine makes and models have different cutting applications
Horsepower ratings affect the ability to cut some materials Variable #11 Wheels
Proper adjustment of the wheels can create variable band performance. There are typically two wheels on a band saw machine, and they should be checked for:
9proper alignment 9bearing condition 9flange condition. Variable #12 Machine Condition
Machine condition, good and bad, can create a high degree of variation in band saw cutting productivity and accuracy.
Is the machine old?
Is the machine new?
Has the machine been well maintained? Variable #13 Proper Vises
Vises hold work firmly to allow accurate cutting
Proper alignment of the vice will allow square cuts…
…Improper alignment of the vice will create crooked cuts Variable #14 Guides
Guides should support and align the band. When properly adjusted they…
*Maintain a cut versus a cut
*Reduce Variable #15 Guide Arms
Guide arms should be as close to the work as possible, and secured firmly
When the adjustable guide arm is too far away from the work, the blade can be damaged Variable #16 Brushes
Brushes aid in the cleaning of chips from the gullet of the band, which helps prevent tooth stripping and leaves smoother cut surfaces
The ends of the brush filaments should 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 Cutting Fluid
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
Run band saw cutting fluid much RICHER for turning, drilling, or grinding! Variable # 18 Material Machinability
The “toughness” of metal can vary tool life. Material can look the same, but vary greatly in it’s machinability.
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 machinablity 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 band
• 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 Variable #21 Production Requirement
What is your requirement? Is it pieces on the floor or life?
When making a selection, 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 Variable #22 Room Temperature
Room temperature can affect the hydraulic fluids that are in the machine
***A Monday morning blade startup after a cold weekend will cause the machine to run with less aggression – give the saw and the hydraulic fluids a chance to warm up!*** SIMONDS 22 VARIABLES… A REVIEW • The Operators‐ The largest variable • The Number of Teeth in the Band‐ 3 minimum, 6‐12 optimum, 24 maximum • Tooth Style‐ Standard, Skip, Sabre, or Variable Pitch. • Tooth Set‐ Regular, Wavy, Every Tooth Set, or Modified Raker. • Band Tension‐ Measured with the patented Simonds Simometer. • Band Speed‐ Start with the manufacturer’s recommendation. • Break‐In Procedure‐ Reduce normal feed rate by ½ • 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 barely turn by hand. • Guide Arms‐ Should be as close to the work as possible for support. • Brushes‐ Aid in the cleaning 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‐ Structural and small solids tend to be harder on the band. • Production Requirement‐ Continuous vs. intermittent use. • Room Temperature‐ Affects hydraulic fluids in the machine. Any one variable or any combination of the above variables can affect band saw life!