Circular saw blades with brazed carbide teeth were first used on plate saws to cut steel plates at Ingersoll Milling Machine Co. (Rockford, Illinois) in 1963. The basic geometry with positive cutting angle of the carbide teeth was taken from aluminum circular saw blades, but the tool life was not economical for cutting steel billets.
In the late 1960’s, the University of Braunschweig (Germany) developed a new geometry for cutting steel with 18 degrees negative cutting angles and chamfered all of the cutting edges to avoid sharp corners to prevent breakage. This geometry was successfully applied on the first billet saw in 1969, developed by Advanced Machine & Engineering Co. (AME) in Rockford (ref. Sawing Academy www.ame.com/Sawing-Academy “History of Carbide Saws”).
The heat from the cutting process, especially using negative cutting angles when cutting steel, transfers to the chip, causing it to expand and jam in the slot. This can be prevented by splitting the chip. There are two common tooth geometries developed to split the chip: “Triple Chip” and “Notch Grind.”
Triple Chip (High Low Geometry)
Triple chip geometry (Figure 1) splits the chip into three parts. The first tooth is about .013” higher than the second tooth and cuts the center of the slot, and the second tooth cuts the remaining two sides, which creates three chips. The triple chip geometry allows a pair of teeth to cut the width of the slot, but only the secondary teeth guide the blade into the slot. This geometry has been very successful in cutting solid steel billets because it reduces vibration and creates a quieter cut.
Notch Grind (2-Geometry Chip)
The newer notch grind geometry was developed by Horst Döpke at Braunschweig University for cutting tubing, pipes, or profiles. The chip of each tooth is split by a groove on the cutting face. (see Figure 2)
A similar geometry was developed and patented in 1984 (patent #4,463645) by Goellner for Speedcut, now AMSAW, to cut solid billets at a higher cutting rate. The advantage was that each single tooth split the chip and stabilized each tooth by side guiding, improving the tool life.
Every tooth is guided in the slot compared to every other with the triple chip geometry. This cutting process is better for interrupted cuts, because more teeth are guiding on their sides, which reducing vibrations and improving tool life. Notch grind geometry also increases cut rates, making it the preferred geometry for billet sawing as well. Surprisingly, the notch has no negative cutting effect.
Higher cutting rates, however, require a more rigid saw with more power, so not every saw will cut efficiently with notch grind saw blades.
Key Take Away:
With a rigid carbide saw, the notch grind geometry allows you to cut the entire range of solid and structural profiles at faster rates and better tool life.
If you’re not getting the tool life you expected from your circular saw blade and you need help troubleshooting the problem, find your answers in our Sawing Academy articles, or contact one of our production sawing experts.
It's only fair to share...