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

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

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

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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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? • 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!

  8. Variable #7 • Break-In Procedure • 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 • 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 speedis 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 Remember . . . Proper break-in for your bandsaw blade will greatly improve bandsaw blade cutting life. Be sure to always take a chip!!

  9. 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? • Determine the material that you are cutting • Decide which band saw blade to use (carbon, bimetal, carbide) • Consult a feed rate chart for the material being cut, and set the saw’s feed pressure accordingly

  10. 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-30 M-2 M-42 Shock resistance in a tooth tip is a tradeoff . . . . . . Long wear versus low shock resistance Shock Resistance vs. Wear Resistance Resistance to shock Resistance to wear S h o c k W e a r Increase in Rockwell hardness of tooth tip Carbide Tipped Carbon M-2 M-30 M-42

  11. 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

  12. 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

  13. 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?

  14. Variable #13 • Proper Vises Vice Adjustment – Front View Band Saw Blade 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 MovableVice Machinist’s Square Saw Bed Vice Adjustment – Top View Movable Vice Machinist’sSquare Fixed Vice Band Saw Blade Adjust fixed vice to square with band saw blade Band Saw Squareness – End View Machinist’s Square Fixed Vice Alignment Tool Band Saw Blade

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

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

  17. 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 constantlyrub the side of the blade

  18. Variable #17 • Coolant Should . . . Washchips out of the blade’s gullets Coolthe tooth tips to reduce heat damage Lubricatethe cut to reduce heat caused by cutting friction Coolant . . . to Wash Cool Lubricate

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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!

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