The saw formulas presented are based on imperial measurements:

Power

Power (hp) required is a function of feed speed, saw design and specific gravity of the wood being sawn.  Increasing any of the variables will increase the horsepower required.

• Feed Speed [fpm] x (Depth of Cut Inside Saw [inches] + Depth of Cut Outside Saw [inches]) x Kerf [inches] x Specific Gravity x 100 ÷ 144 ÷ Arbor Drive Efficiency x 100
• Specific Gravity: Douglas Fir = .45, Oak = .60, Southern Yellow Pine = .47, Spruce = .37, Oak = .60

Feed Speed

Feed Speed (fpm) constrains is a function of horsepower, saw design and specific gravity of the wood being sawn.  Increasing any of the variables will increase the feed speed constraint.

• Minimum (Max Feed Speed [fpm], Horsepower ÷ (Depth of Cut Inside Saw [inches] + Depth of Cut Outside Saw [inches]) ÷ Kerf [inches] ÷ Specific Gravity ÷ 100 x 144 x Arbor Drive Efficiency ÷ 100, Gullet Area [sq. inches] ÷ Sawdust Expansion Factor ÷ Depth of Cut Inside Saw [inches] x (Rim Speed [fpm] ÷ Tooth Pitch [inches])
• Specific Gravity: Douglas Fir = .45, Oak = .60, Southern Yellow Pine = .47, Spruce = .37, Oak = .60

Rim Speed

Saw rim speed (feet per minute) is the speed of the saw blade.  This is determined by the rpm of the abor and the diameter of the saw.  The faster the saw speed the more teeth per minute in the cut.

• Saw Diameter [inches] x 3.1416 ÷ 12 x RPM

Tooth Pitch

Tooth pitch (inches) is the tip to tip distance between teeth.

• Saw Diameter [inches] x 3.1416 ÷ # of Teeth

Tooth Bite

Tooth bite (inches) is determined by the feed speed, the rpm of the saws and the number of teeth.  Increasing the feed speed will increase the tooth bite.

• Feed Speed [fpm) x 12 ÷ RPM ÷ Number of Teeth

Gullet Area

Gullet area (square inches) determines the amount of sawdust that the gullet will hold.  Increasing gullet size (with the same number of teeth) will allow the saw to be fed faster.

• Saw Diameter [inches] x 3.1416 ÷ Number of Teeth x Gullet Depth [inches] x Gullet Area Factor
• Gullet area factor = 0.42 for square back tooth 0.52 for round back tooth.

Gullet Capacity

Gullet capacity (square inches) is a function of gullet area and sawdust expansion factor.  Fast growing species such as southern yellow pine take up more gullet space due to the size of the sawdust “chunk”.

• Gullet Area [square inches] ÷ Sawdust Expansion FactSawdust expansion factor: 1.8 to 2.0 for slow growing species (ie. northern spruce/pine), 2.5 for fast growing species (ie. southern yellow pine).

Gullet Fill

Gullet fill % is determined by the depth of cut and the tooth bite.  This calculation is used to determine available gullet fill capacity.

• Depth of Cut [inches] × Tooth Bite [inches] x Sawdust Expansion Factor ÷ Gullet Area [square inches] × 100
• Sawdust expansion factor: 1.8 to 2.0 for slow growing species (ie. northern spruce/pine), 2.5 for fast growing species (ie. southern yellow pine).