Lubrication Flashcards
What are the 3 types of friction
Sliding, Rolling, and Fluid
What kind of force causes unlike materials to stick together?
Adhesion
What kind of force cause molecules of like materials to stick together
Cohesion
When adhesive forces are strong oils rich in these molecules are said to be high in what?
Oiliness
What is the resistance to flow?
Viscosity
What happens when oil temperature rises?
Viscosity drops, oil thins out
What viscosity is a measure of viscosity affected by the density of the oil?
Kinematic
What is the most common method of measuring viscosity
Saybolt viscosimter
The higher the VI number the _______ the change in viscosity due to temperature
Smaller
Efficiency of the oil wedge depends on what?
Load, RPM, operating temp, clearance, viscosity, volume of lubricant, shaft surface finish
When the film of oil fails for a short time it’s called what?
Boundary lubrication
If you over lubricate a threaded hole what can happen?
Hydraulic lock
Additives and inhibitors are divided into these three groups
Air control, water control, load capacity control
Where are detergents usually found?
Gas and diesel engines
What are the two types of oil lubrication systems?
Once-through and enclosed
How to do you make approximate oil check?
Smell, touch, sight, magnet
What are greases generally thickened with?
Soap
Soap content for general greases are what percentage?
7% to 18% (low as 3% high as 50% for special greases)
What soap greases are good for damp conditions?
Calcium
What soap greases are good for dry conditions?
Sodium
What soap greases are good for water resistance, high temps, and most commonly used?
Lithium and Barium
What greases are recommended for high shock load nd high pressure?
EP extreme pressure
NLGI penetration numbers range from what?
Softest 000, 00, 0, 1, 2, 3, 4, 5, 6 Hardest
The temperature at which a grease becomes fluid enough to drip is called what?
Dropping point
When grease tends to shear in the direction of rotation is is called what?
Directional fluidity
How do you initially pack a bearing?
By hand
How full do you pack a bearing housing?
One-third full for high speed, One-half full for slow speeds
A single reduction required a _____ oil to suit the input gears
Light oil
A compound needs a _______ oil to suit the output gear mesh
Heavier oil
In an oil bath how high does the fluid go?
Covers the outer race but does not cover the centre point of the lowest ball or roller
Over oiling produces what?
Churning and temperature rise
Is oil or grease better for heavy loads at slow speeds?
Grease
What is a good lubricant for very high speeds?
Oil
What cutting oils can only be used on ferrous metals?
Active