2. VARIABLES WHICH AFFECT BANDSAW BLADE LIFE A practical overview of bandsawing basics

3. Variable #1 The Operators 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

4. Variable #2 Number of Teeth in Band Number of Teeth in Band Too few teeth... tooth straddle, which can cause tooth strippage Too many teeth... loads the gullet, which can cause tooth strippage The 3 Tooth Rule 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

5. Variable #3 Tooth Style Tooth Style Skip 0 degree rake and shallow gullets Good for cutting large sections of soft, non ferrous metals and wood Regular Rake angle of 0 degrees, full round gullets Used for cutoff and contour cutting - general purpose 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

6. Variable #4 Tooth Set Tooth Set Regular Raker Set O ne 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 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 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

7. Variable #5 Band Tension 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.

8. Variable #6 Blade Speed 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.determine the length of the band saw blade 2.mark a spot on the blade (or locate the weld) 3.start up the saw 4.time one rotation of the blade (in seconds) 5.divide the number of seconds for one rotation into 60 seconds 6.multiply the result by the length of the blade * The answer is the Surface Feet Per Minute!

9.  What is a proper break-in? Reduce the normal feed rate by 1/2 Recommended Band Speed in SFPM:300 250 200 150 100 50 Square inches to cut for break-in:90 75 60 40 25 10 Variable #7 Break-In Procedure Break-In Procedure Remember... Proper break-in for your bandsaw blade will greatly improve bandsaw blade cutting life. Be sure to always take a chip!!  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. Band Saw Blade Tooth Tips Magnified Proper Break-in Improper Break-in Reduced feed pressure ‘hones’ the cutting edge of the tooth Excessive feed pressure ‘breaks down’ the sharp tooth edge prematurely

10. Variable #8 Feed Rate Feed Rate Feed rate is measured in Square Inches per Minute (SIM) 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 Feed Rate too light Rubs the tooth dull Feed Rate too heavy Premature tooth wear Recommended Feed Rate Optimum blade life

11. Variable #9 Blade Quality 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-MetalCarbide Tipped An example of blade type differences are Red Hardness and Shock Resistance: Shock resistance in a tooth tip is a tradeoff...... Long wear versus low shock resistance The relative Red Hardness of tooth tips Temperature Tolerance Range of Cutting Edges Rc Carbon M-2 M-30 M-42 Carbide Tipped Resistance to wear Resistance to shock Increase in Rockwell hardness of tooth tip Shock Resistance vs. Wear Resistance ShockShock WearWear CarbonM-2M-30M-42 Carbide Tipped

12. Variable #10 Machine Type 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

13. Variable #11 Wheels 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 WheelDrive Wheel Idler Wheel Alignment Correct Tracking Improper Tracking, SlippageBlade Breakage, Flange Wear

14. Variable #12 Machine Condition 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?

15. Variable #13 Proper Vises Proper Vises Why vises?... To hold work firmly and accurately. Proper alignment of the vice will allow square cuts...... Improper alignment of the vice will create crooked cuts Band saw blade squareness also affects the straightness of the cut Vice Adjustment – Top View Vice Adjustment – Front View Band Saw Blade Machinist’s Square Saw Bed Movable Vice Adjust fixed vice to square with band saw blade Fixed Vice Machinist’s Square Movable Vice Band Saw Blade Alignment ToolFixed Vice Band Saw Blade Machinist’s Square Band Saw Squareness – End View

16. Variable #14 Guides Guides should support and align the blade, when properly adjusted they...... and reduce vibration maintain a STRAIGHT versus a cut...

17. Variable #15 Guide Arms Guide Arms Guide arms should be as close to the work as possible, and secured firmly...move the adjustable guide arm in! When the adjustable guide arm is this far away from the work, the blade can be damaged... Here’s an example of how properly adjusted guide arms should look... snug to the work piece Wrong! Correct!

18. Variable #16 Brushes Brushes  Brushes aid in the clearing of chips from the gullet of the blade, which helps prevent tooth strippage and leaves smoother cut surfaces  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 Band Saw Brushes are very Important!

19. Variable #17 Coolant 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

20. Variable #18 Material Machinability Material Machinability The “toughness” of metal can vary tool life. Materials 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 Cold Rolled Stainless Inconel

21. Variable #19 Material Hardness 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

22. Variable #20 Material Shape Material Shape  Structural material and small solids tend to be harder on the blade The shape of the work piece can affect cutting performance...  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

23. Variable #21 Production Requirement Production Requirement 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 Piece lots? Short production runs? Production cutting – long runs?

24. VARIABLES... A REVIEW 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!