Lubrication

Question 1

What are the 3 types of friction?

Answer 1

Sliding friction

Rolling friction

Fluid friction

Question 2

Describe sliding friction?

Answer 2

Sliding friction occurs when two surfaces slide over each other.

Question 3

Describe rolling friction?

Answer 3

Rolling friction occurs when a spherical or cylindrical body rolls over a surface

Question 4

Describe fluid friction?

Answer 4

When lubricant oil is applied to two surfaces in contact, a film of oil is formed. Filling up depressions and covering projections on both surfaces.

Because there is no metal on metal contact sliding occurs between the layers of oil.

Question 5

What is lubrication?

Answer 5

The reduction of friction to a minimum by the replacement of dry friction with lubrication.

Question 6

What is viscosity?

Answer 6

Viscosity is the resistance to flow. Oils with high viscosity are thicker and pour more slowly then those of lower viscosity.

Question 7

What is the most important property of lubricating oil?

Answer 7

Viscosity

Question 8

Choosing the best viscosity oil depends on what?

Answer 8

Speed (RPM)

Load

Temperature

Pressure

Environment

Question 9

What are the two ways viscosity it measured?

Answer 9

Dynamic - determined by the force required to overcome fluid friction in a film of known dimensions

Kinematic - the measure of viscosity that is affected by the density of the oil.

Question 10

Describe oil wedgeing?

Answer 10

Clearance in a bearing is taken up by oil.

As the shaft rotates oil climbs side of bearing. Moving in the opposite direction.

Eventually oil surrounds entire shaft

At full speed oil enters the area of lowest pressure

Now the shaft carries the oil in the same direction toward the area of maximum pressure.

Now an oil wedge is formed pushing the shaft up toward the centre of the bearing.

Question 11

Efficiency of the oil wedge depend on what?

Answer 11

Load

Rubbing speed Or rpm

Operating temperature

Clearance between surfaces

Oil viscosity

Volume of lubricant

Where lubricant is introduced

Shaft surface finish

Question 12

Boundary lubrication occurs when?

Answer 12

The film of oil fails for a short time.

Question 13

What can cause hydraulic locking?

Answer 13

Over lubricating

Question 14

Oxidation occurs because?

Answer 14

All petroleum and vegetable oils chemically react with oxygen.

Oxidation is increased by high temperatures, air, contaminants or water.

Question 15

What are the two waste products oxidation produces?

Answer 15

Oil-insoluble materials such as varnish or sludge

Oil-soluble acids

Question 16

Describe demulsibility?

Answer 16

The ability of a petroleum oil to separate from water upon standing.

It can be increased by additives

Question 17

Describe Emulsibilty?

Answer 17

The ability of a petroleum oil to mix with water using a special emulsifying agent.

Question 18

What does a rust inhibitor do?

Answer 18

Helps reduce the rusting of ferrous parts in the system.

Question 19

What are the two types of oil lubrication systems?

Answer 19

A once through system

Or

Wasted oil system

Question 20

Splash lubrication is most common in?

Answer 20

Enclosed gear systems

Question 21

Worm gears and moderate speed chains are lubed by?

Answer 21

Running through an oil bath

Question 22

High speed bearings and high velocity roller chains use a?

Answer 22

Oil mist system.

Question 23

When doing an approximate oil quality you would check for?

Answer 23

Smell

Touch

Site

Question 24

EP (extreme pressure) grease is used for?

Answer 24

Shock loaded or high local pressure areas

Question 25

NLGI grades are measure by?

Answer 25

Numbers 00 -6. Six being the hardest.

Question 26

What precautions are taken when using different grease?

Answer 26

Don’t mix grease from different manufactures

Don’t mix various grease grades

Don’t use extra additives

Question 27

Describe the procedure for hand packing bearings?

Answer 27

Fill the spaces between the rings with grease after assembly

Pack the housing 1/3 full for high speeds and 1/2 full for slow speeds

Do not over pack with grease.

Question 28

Open gears are lubricated with a grease or a heavy oil what conditions must you consider?

Answer 28

Temperature

Method of application

Environment

Gear materials

Choice of lubricant

Question 29

What factors are considered for enclosed gears?

Answer 29

Load

Operating speed

Operating temperature

Lubrication methods

Type of gear

Environment

Question 30

Oil lubrication is used in what temperatures?

Answer 30

Below 0 to 93 degrees C

Question 31

How much oil do you use in a bearing oil bath?

Answer 31

Oil should cover the bottom of the outer race but does not cover the centre point of the lowest ball or roller

Question 32

What are the advantages of using greased?

Answer 32

Good lubricant for heavy loads at low or medium speeds

Requires relatively simple seals

Provides better start up protection offer short periods of downtime

Gives better protection against rust during periods of downtime.

Tends to stay in place

Question 33

What are the advantages of using oil as a lubricant?

Answer 33

Good for high and very high speeds

Developes less fluid friction than grease

Had a flushing action that pushes dirt and contaminants to the bottom of the housing

Can be used as a heat exchange medium

Can be removed easily from the housing

Question 34

What is the purpose of cutting oil?

Answer 34

Cool the workpiece

Cool the cutting tool

Protect against rust

Prevent welding of metal chips with the tool

Wash away metal chips

Allow high speed cutting for better productivity and surface finish