Misumi USA Engineering Blog

Basic Load Rating in our catalog for each bearing is NOT the actual load that our bearings can withstand. Below is an example of how Basic Load Rating converts to actual load.

Light Load- Up to 0.075C (up to 7.5%)

Medium Load- from 0.075C to 0.15C (between 7.5% and 15%)

Heavy Load- Over 0.15C (Over 15%)

C- Basic Load Rating

Cr- Dynamic Load Rating

Cor- Static Load Rating 

Example: Bearing B6004ZZ (Cr= 9.4KN, Cor=5.05KN)

Actual Radial Load in Motion (Dynamic):

Light Load < 9.4*0.075< 0.705KN< 705N< 71.9kgf< 158.5lbf

Medium Load= 9.4*0.075~9.4*0.15= 0.705KN~1.41KN= 705N~1410N= 71.9kgf~143.8kgf= 158.5lbf~317lbf

High Load > 9.4*0.15> 1.41KN> 1410N> 143.8kgf> 317lbf

Conclusion:

We can see from above calculations that an actual radial load above 317lbf for B6004ZZ bearing is to  operate at a high load. The Misumi blog “Ball Bearing Life and Rated Load” will also help determine bearing life span knowing actual radial and axial load.

Simplified unit conversion table from Metric system (SI) to US unit system.

For metric gears the gear proportions are based on the module. Modules is the ratio of the “Pitch Diameter” to the “Number of Teeth”.

m (module)= d (pitch diameter (mm)) / N (number of teeth)

When module (m) number for metric gears is getting bigger- size of the teeth is getting bigger too.

In the USA the module is not used and instead the “Diametric Pitch” or “Pitch” (p) is used.

p= N (number of teeth) / d (pitch diameter (Inch))

When pitch (p) number for inch gear is getting bigger- size of the teeth is getting smaller.

Calculation example: Having two dimensions for each gear we will try to find number of teeth (N) using above equations:

Metric gear:
Ф (pressure angle)= 20°
m (module)= 0.8
N (number of teeth)= ?
d (pitch diameter)= 16 [mm]

Inch gear:
Ф (pressure angle)= 20°
p (pitch)= 32
N (number of teeth)= ?
d (pitch diameter)= 0.625”

p= N/d ↔ N= p*d ↔ N= 32*0.625= 20

Conclusion: for both spur gears we calculated same number of teeth. Converting inch dimensions to metric (1”= 25.4mm) we can see how close these two gears are:

Knowing pitch (p) for inch gears we can simply calculate inch module:

m= (1”/32)= 0.03125

Or knowing pitch diameter (d) and number of teeth (N):

m= d/N= 0.625/20= 0.03125

Lets convert Inch module m= 0.03125 to metric using (1”= 25.4mm) converter from Inch to Metric dimensions.

0.03125 * 25.4= 0.794

Conclusion: We can see that the metric and inch spur gears are dimensionally very similar but we should not mesh them together duo to small differences developed during design and manufacturing stage.