If you were to look at a blade cutting metal under a microscope, you would see the tooth tip penetrating the work and actually pushing, or shearing, a continuous chip of metal. The angle at which the material shears off is referred to as the “shear plane angle.” This is perhaps the single most important factor in obtaining maximum cutting efficiency.
Generally, with a given depth of penetration, the lower the shear plane angle, the thicker the chip becomes and the lower the cutting efficiency. The higher the shear plane angle, the higher the efficiency, with thinner chips being formed. Shear plane angle is affected by work material, band speed, feed, lubrication and blade design