Gear Shaping Operation

Gear Shaping Operation

Gear Shaping Operation - Gear shaping process makes use of a hardened pillion as a cutter, ground with top rake and clearance. Referring to, gear shaping cutter 1 receives reciprocating movement (in the direction of arrow 1) which is the principal movement. The cutter reciprocates like the cutting tool in a standard shaper but at a rate of 50 to 450 strokes per minute.

A - Gear Blank	A - Gear Blank
B - Gear Cutter	B - Gear Cutter

Gear Shaping Operation

In addition to the reciprocating movement of tbe cutter, both the cutter and blank rotate at the same pitch line velocity. Cutter rotation and gear rotation are marked by arrows III and II respectively. The relative speed of rotation of the cutter and the gear (blank) is the same as the gear to be cut will have with a pinion of same number of teeth as the cutter.

The radial movement in the direction of arrow I-V (radial infeed) is imparted to the shaping cutter when it is to be fed into the depth of cut. The gear cutting cycle is :

(i) Cutter is fed into full depth (by giving radial infeed) with cutter reciprocating and blank stationary.

(ii) Both, cutter and blank slowly rotate about their axis until all the teeth are generated upon the gear blank.

In other words, to provide cutting action the cutter is recipro­cated along its own axis at high speed, and at the same time; a feed advance motion is applied to both the cutter and gear blank (by rotating them slowly), thus presenting different parts of the flanks of the cutter to the gear blank to form the involute profile,

The cutter reciprocating across the blank face, can cut either on the upstroke or downstroke. In Fig. (a), in each downward stroke, the cutter removes some stock out of the tooth space of the blank, thus shaping the gear teeth. To prevent the flanks of the cutter teeth from scoring tbe blank as the cutter is returned upwards, the blank is withdrawn radially in the direction of arrow V and returns automatically to tile initial working position at the beginning of the new working stroke.

As with most gear cutting, the blank is usually Toughed to say three quarter depth, followed by a finishing cut. The generating action of the cutter and the blank is shown in Fig. (C). the fine lines indicating the amounts of metal removed by each cut in a given tooth space.

Fig. (B) shows that both external and internal teeth can be shaped on a gear blank, 'a' is tbe gear blank and 'b' is the cutter. One great advantage of gear shaping is that only one cutter is needed to cut all gears of the same pitch; whereas rotary cutters have no such latitude of application.

Actually a rotary cutter is correct only for the number of teeth for which it is designed and where in practice one cutter is made to cover a range, the sears at the extremity of the range arc necessarily inaccurate. At the same time, the gear shaper process is much faster than rotary cutting.