Shaft manufacturing, materials and

shapingCourse: Machine Elements 1Student: Subkhiddin Mukhidinov ID: 47816

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.

MaterialsThe 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

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.

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.

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.

Property of materialsMaterials 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

Tolerance on the Gears

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

Key sizes for English Shafts

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.

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.

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.

Jumbo drilling• A shower prevents

overheating when the jumbo drill has its turn, it bores a hole right through the middle of the blank.

Jumbo drilling

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.

Drilling holes

• Then the blank goes into a computer-controlled mill.• The mill drills holes

through which lubrication will flow when it is operating

Stamping

• When the blade comes off the mill, it stamped with company name and part number.

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.

External Teeth• The computer-

controlled machine that cuts them is called a gear harbor. The gear turns against it as it cuts.

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.

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.

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

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.

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.

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.

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.

Soaking• A soaking in oil

afterward hardens the metal.

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.

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.

The End