A SEMINAR REPORT ON GEAR FINISHING METHODS

PESENTED BY:- KETAN PATEL

GUIDED BY:-

WHY GEAR FINISHING NECESSERY

None of the methods of gear manufacturing on any

machine produce gears of very accurate dimensions and

shape. Any error crept in the gears during production for

any reason lead to noisy performance of the gear box.

Irregular wear of the teeth and uneven load distribution on

the teeth are the factors enough to cause an early failure of

the gears.so applying methods of finishing after the gear

have been cut on the machine.

GEAR SHAVING:- Gear shaving is a finishing operation that removes small

amounts of metal from the flanks of gear teeth. Gear shaving

may correct small errors in tooth spacing, helix angle, tooth

profile and concentricity.

Shaving improves to be finish on tooth surfaces and can

eliminate tooth end load concentration, reduce gear noise and

increase load carrying capacity.Shaving has been successfully

used in finishing gears of diametric pitches from 180 to 2.

Shaving is done by two methods (1) rack shaving (2)rotary

shaving

RACK SHAVING:-

(i) Rack shaving in which a

rack type shaving tool is

reciprocated under the gear

and in feed takes place at

the end of each stroke. 150

mm is the maximum

diameter of gear that can be

shaved by the rack method.FIGURE:-1 RACK SHAVING

ROTARY SHAVING:-

□In Rotary shaving, the cutter has the same basic form as the rough cut gear. The teeth of the cutter have grooves cut across the flanks in planes at right angles to the axis of the cutter; these grooves form the cutting edges, but because only a small amount of metal between 0'03 and 0'08 mm is to be removed.

FIGURE:-2 ROTARY SHAVING

GEAR BURNISHING Burnishing is applied to unhardened gears for

finishing to very accurate dimensions. In this method the machined gear is rolled under

pressure with three hardened master gears of high accuracy and finish.

Though the method provide smooth and accurate tooth profile but due to localized residual stress.

It is very advisable to employ the method on precision gears.

GEAR GRINDING:-

Grinding is a very accurate method and is, though relatively

expensive, more widely used for finishing teeth of different type

and size of gears of hard material or hardened surfaces.

Hardened gears are difficult to finish by shaving and burnishing

methods.

Like gear milling, gear grinding is also done on two principles

(i) Forming

(ii)Generation, which is more productive and accurate

Gear lapping

The object of employing the lapping process for finishing

gears is to achieve high degree of finish.

The gear to be finished after machining and heat treatment

and even after grinding is run in mesh with a gear shaped

lapping tool or another mating gear of cast iron.

Lapping can remove very small amount of metal and correct

small errors up to 0.05mm.

GEAR HONING:- Gear tooth honing is a gear finishing process that improves the surface

finish of the tooth profile and reduces the noise of spur and helical gears

after heat treatment.

Gear honing is a finishing method for hardened gears The grain size of

the abrasive with which it is charged is selected to suit the honing

allowance (0'025 to 0.05 mm) and the surface finish requirements. The

work gear is meshed with the honing tool in a crossed axis relationship.

There is no in feed mechanism. The gear is run in both the directions

during the process. Gear tooth honing can be carried out with either a constant pressure

between teeth of the gear and honing tool