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# Saw Design Formulas

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These are the formulas used to design and select circular saws and bandsaws.   For now, only the formulas and the definition of the variables are given.   Later we will add a more complete explanation of what these formulas mean.

### Saw and Tooth Shape

d          Circular saw diameter or bandmill wheel diameter (inch)

z           Distance between centers of bandsaw  wheels

P          Tooth pitch (inch)

n           Number of teeth

k           Kerf

h           Thickness of saw plate

s           Side Clearance (inch)

sMIN     Minimum recommended side clearance (inch)

a           Gullet area (sq. inch)

### Operating Conditions

N          Shaft speed (rpm)

c           Blade ( or rim) speed (sfpm)

b          Bite per tooth (inch)

D         Depth of cut (inch)

f          Feed speed (fpm)

fMAX    Maximum recommended feed speed (fpm)

fMIN     Minimum recommended feed speed (fpm)

### Performance Prediction

GFI          Gullet Feed Index  = Volume of wood removed by a tooth

---------------------------------------------

Volume of tooth gullet

GFIMAX    Maximum allowable Gullet Feed Index

= 0.3 for circular saw

= 0.7 for bandsaws

### Power Consumption

E                Estimated power required (hp)

C                Energy factor depending on wood properties

C = 35 for North American softwoods

= 40 for dry fir

= 70 for hardwoods

### Evidence from the Wood

X        Distance taken by ‘m’ bites on a board

m

# Formulas

3.14 x d x N                                   12 x c

c = -------------------------         or      N = -----------------

12                                              3.14 x d

b = X / m                                or          X = m x b

## For Bandsaws only......

L = 2 x z + 3.14 x d

### For Circular saws only………

3.14 x d                                   3.14 x d

P = -----------------         or      n = -----------------

n                                              P

12 x f                                          b x n x N

b = -------------             or          f = -------------------

n x N                                              12

## For Circular and Bandsaws.....

b x c                                  f x P

f = -----------         or          b = -----------

P                                       c

b x D                              GFI x a                         GFI x a

GFI = ------------      or     b = -----------------    or      D = -----------------

a                                      D                                   b

f x D x P                                         GFI x a x c

GFI = ------------------         or           f  =   ---------------------

a x c                                                  D x P

GFIMAX x a x c

fMAX = -----------------------------

D x P

s x c                                                      f x P

fMIN = -----------     ( b = s )     or      sMIN = -----------

P                                                         c

k - h

s = ----------    or     k = h + 2 x s

2

C x k x f x D

E = -------------------------

144