Gear Shaving

Gear Shaving

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 tbe 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 diametral pitches from 180 to 2.

Operation:

Shaving is done by two basic methods

(i) Rack shaving in which a rack type shaving tool is reciprocated under tbe gear and in feed takes place at tbe end of each stroke. 150 mm is the maximum diameter of gear that can be shaved by the rack method.

Gear Shaving Machines

Gear Shaving Operation

Rotary Gear Shaving Cutter

Principle of Gear Shaving Machine

(ii) 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, they merely shave the teeth, As shown in Fig, the semifinished gear, which is mounted on live centres, is brought into mesh, and power is applied to the shaving tool to drive gear.

When in mesh and rotating, the tool passes axially so as to process the whole width of the gear, The number of passes-complete movements across the gear face ­is usually two, four or six. The teeth are crowned by a slight rocking 2, action of the cutter, to give gears the proper running clearance during service. In Fig, (b), the workpiece is a gear cluster, 3-nd the machine is set up for only one of the gears on it.

In Fig, (d), gear shaving cutter 4, is set an angle with respect to the axis of work gear 5, (to be shaved) and is driven at a speed of 250 rpm, Work gear is held between centres on mandrel 6, To extend the cutting action over the whole length of the gear teeth, table 8 reciprocates at a rate of 0'1 to 0'3 mm;) per revolution of the work gear. At the end of each stroke, the table has an infeed of 0'02 to 0'04 mm before it starts its reverse stroke.

If teeth are to be crowned, use is made of rocking plate 7 which has bracket 3 that carries pin 1. Pin 1 slides along the inclined slot of cam 2 and thereby rocks plate 7 with the work gear. This crowns the gear teeth by shaving them slightly thinner at the ends than at the middle of tbe gear face.