formula
BASIC LUBRICATION FORMULAS
V = A x T
V = volume in terms of lube-oil replacement rate in cubic inches per hour (in³/hr)
A = bearing surface area in square inches (in²) (sized differently based on bearing type)
T = film thickness….generally .001 inch….but it may vary based on oil type and application
V = A x T
V = volume in terms of lube-grease replacement as cubic inches per four hour (in³/4 hrs)
A = bearing surface area in square inches (in²) (sized differently based on bearing type)
Quite often requirements are expressed in metric terms. To convert to metric, calculate volume requirements as noted above and simply multiply by 16.39 to convert to cubic centimeters per hour (cc³/hr) for oil or cubic centimeters per four hours (cc³/4 hrs) for grease.
- Plain bearings: Area (in²) = 3.14 x shaft diameter (ins) x length of bearing (ins)
- Slides, gibs and ways: Area (in²) = area of the largest contact surface
- Anti-friction bearings: Area (in²) = shaft diameter squared x number of rows
Area (in²) = 3.14 x 6 (ins) x 6 (ins) = 113.04 in²
Volume (in³/hr) = 113.04 (in²) x .001 (in) = .113 (in³/hr)
Should this need to be converted to metric, the requirement for this single bearing application would be 1.85 cubic centimeters per hour. .113 (in³/hr) x 16.39 = 1.85 (cc³/hr)
Each and every bearing or lube point on a machine would be calculated in this fashion and when done, the replacement rates for all points would be added together to determine the total system lubrication requirement.
