2. What is Shaft or Gear?
• A shaft or gear is a wheel
with teeth that meshes with
the teeth of another shaft to
transmit power on a
continuous basis
• Combining shafts of
different diameters affects
rotation speed and force.
3. Materials
The gear material should have
the following properties:
• High tensile strength to prevent
failure against static loads
• High endurance strength to
withstand dynamic loads
• Low coefficient of friction
• Good manufacturability
4. Materials
• The materials used for the manufacture of gears depends upon the
strength and service conditions like wear, noise etc.
• The gears may be manufactured from metallic or non-metallic
materials. The metallic gears with cut teeth are commercially
obtainable in cast iron, steel and bronze.
• The non-metallic materials like wood, rawhide, compressed paper
and synthetic resins like nylon are used for gears, especially for
reducing noise.
5. Cast Iron
• The cast iron is widely used for
the manufacture of gears due
to its good wearing properties,
excellent machinability and
ease of producing complicated
shapes by casting method.
• The cast iron gears with cut
teeth may be employed, where
smooth action is not
important.
6. Steel Gears
• The steel is used for high strength
gears and steel may be plain carbon
steel or alloy steel.
• The steel gears are usually heat
treated in order to combine properly
the toughness and tooth hardness.
7. Property of materials
Materials Condition Brinell Hardness Number Minimum Tensile
Strength (kg/cm2)
Malleable cast iron
(White heart castings,
Grade B)
- 217 max. 2800
Cast Iron
(Grade 20)
As cast 179 min 2,002
Cast steel - 145 5,500
Carbon steel
(0.3% carbon)
Normalised 143 5,000
Carbon steel
(0.3% carbon)
Hardened and Tempered 152 6,000
Carbon chromium
steel (0.4% carbon)
Hardened and Tempered 229 8,000
9. Key and Keyway on Gears
• A key is a machine element used to
connect a rotating machine element to
a shaft.
• The key prevents relative rotation
between the two parts and may
enable torque transmission.
• For a key to function, the shaft and
rotating machine element must have
a keyway and a keyseat, which is a slot
and pocket in which the key fits. The
whole system is called a keyed joint
11. First Step of Production
• Production begins with a
large round bar of high-
grade steel, which
contains a certain amount
of carbon to make it even
stronger.
12. Slicing required size of metal
• An automated band saw
slices off a piece that has
the right thickness for the
size of shaft they are
making.
13. Shaping
• They mount the blank on a
computer-controlled blade as
it spins a turret carrying a
series of carbide tools moves
in.
• One tool after another takes its
turn machining the blend to a
specific shape.
14. Jumbo drilling
• A shower prevents
overheating when the jumbo
drill has its turn, it bores a
hole right through the
middle of the blank.
16. Carving the groove
• The last tool carves a
groove on the front
of the blank.
• After this process the
shaft should be
waited for a while.
17. Drilling holes
• Then the blank goes into a
computer-controlled mill.
• The mill drills holes through
which lubrication will flow
when it is operating
18. Stamping
• When the blade comes
off the mill, it stamped
with company name and
part number.
19. Internal Teeth
• A machine called a gear shaper
carves out the energy to one's lining
the center hole with its titanium
coated cutter.
• The machines other components
keep the cutter movement correctly
time.
• The number of teeth and sizes vary
from gear to gear, so for each model
they have gear shaper with a
specific cutter.
20. External Teeth
• The computer-
controlled machine
that cuts them is
called a gear harbor.
The gear turns
against it as it cuts.
21. External Teeth
• If the harbor would cut the full
depth of the teeth at one shot
the cutter would break
• So the gear keeps turning
around and around again as the
harbor cuts a bit more with each
pass until the teeth get the right
depth.
22. Measurement Process
• Then the gear undergoes a
computerized inspection.
• A probe scans the entire
surface including every tooth.
• It sends data to a computer
which then analyzes the
dimensions and ensures they
meet the engineering
specifications.
23. Heat Treatment
• Shafts which past this quality-
control inspection, go into a furnace
for heat treatment.
• This strengthens the steel.
• When the furnace reaches a certain
temperature, they inject carbon
inside.
• The shaft absorbs it and the steel
strengthens even further.
Carbon Steel for Structural Machine Usage
Chrome-molybdenum Alloy Steel
24. Quenching
• Quenching is a treatment performed on
steel, applying rapid cooling after heating at
high temperature. Quenching is applied to
adjust the hardness of steel. There are
several types of quenching in accordance
with cooling conditions; oil quenching,
water quenching, and spray quenching.
• After quenching, tempering must be
applied to give toughness back to the steel,
that might become brittle. Quenching
cannot harden genuine steel, however,
quenching can work for steel containing
more than 0.35% carbon.
25. Thermal Refining
• Thermal Refining is a heat
treatment applied to adjust
hardness / strength /
toughness of steel.
• This treatment involves
quenching and tempering.
Since machining is applied to
products after thermal
refining, the hardness should
not be raised too high in
quenching.
26. Induction Hardening
• Induction Hardening is a heat treatment
performed to harden the surface of the
steel containing carbon more than
0.35%, such as S45C or SCM440.
• For gear products, induction hardening
is effective to harden tooth areas
including tooth surface and the tip,
however, the root may not be hardened
in some cases.
• The precision of gears declines by
induction hardening. To encourage the
gear accuracy, grinding must be applied.
27. Carburizing
• Carburizing is a heat treatment
performed to harden only the
surface of low-carbon steel. The
surface, in which carbon is
present and penetrated the
surface, gets especially
hardened. Inner material
structure (with low-carbon
C=0.15%) is also hardened by
some level of carburizing,
however, it is not as hard as the
surface.
29. Grinding
• Heat treatment however
distort steal somehow so
each shaft now goes to a
computer-controlled grinder.
• It restores them to very
precise specifications for
bearing to fit properly.
30. Extra Info
• Shafts are manufactured in various sizes and not only steel, they are
made also from materials such as nylon, aluminum, brass and stainless
steel.
• Some shafts have straight teeth others angle teeth, which makes less
noise when turning.
• Shafts are an essential component in everything, from watches to
heavy mining equipment.
