Figures of feed motion of hob show the cutting of teeth on the work piece with the hob. There are three principal feed motions with respect to the work piece [Figs. 5 (a), (b) and (c)]. Feed motion in the direction OR is the radial-feed motion. It is called radial because it is in the radial direction of the work piece. Feed motions in the directions of OA and OT are called axial-feed motion and tangential-feed motion, respectively. There can be feed motions which are combination of any two of these primary feed motions.
Axial feed is the most commonly used feed, unless there is restriction for axial motion. The hob is fed to the full depth form and then fed in axial direction to generate the full width of the gear.
Radial feed is used where there is restriction to axial motion, for example, in cutting distributor gear on cam shaft, where there is obstruction on both sides of the gear due to the presence of the cam lobes. In this case the hob is fed in radial direction. It can be seen from Fig. 5 (a) that the tooth depth is not constant along the axis. For this reason, the hob has to be set centrally with respect to the gear being cut. In tangential feed, the hob moves at a direction tangential to the gear being cut. This method of cutting is used for producing worm wheels.
When any two of these feeds are used together, we get a resultant feed which is dependent on the ratio of the two feeds. The most commonly used combined feed is called diagonal hobbing in which tangential and axial feed are used simultaneously. This is shown in fig. 6 normally in radial and axial feed, about 1½ to 3 tooth-pitches do the work, whereas in diagonal hobbing more number of teeth are in operation. Accuracy of the gear produced b diagonal hobbing depends on the accuracy of the hob over the number of teeth, and its pressed over number of teeth. As in radial and axial feed only a limited number of teeth do the actual cutting, the wear of they hob will be concentrated only on these few teeth. In order to spread this wear over all the teeth of the hob, many machines are fitted with automatic hob shift.
Axial feed is the most commonly used feed, unless there is restriction for axial motion. The hob is fed to the full depth form and then fed in axial direction to generate the full width of the gear.
Radial feed is used where there is restriction to axial motion, for example, in cutting distributor gear on cam shaft, where there is obstruction on both sides of the gear due to the presence of the cam lobes. In this case the hob is fed in radial direction. It can be seen from Fig. 5 (a) that the tooth depth is not constant along the axis. For this reason, the hob has to be set centrally with respect to the gear being cut. In tangential feed, the hob moves at a direction tangential to the gear being cut. This method of cutting is used for producing worm wheels.
When any two of these feeds are used together, we get a resultant feed which is dependent on the ratio of the two feeds. The most commonly used combined feed is called diagonal hobbing in which tangential and axial feed are used simultaneously. This is shown in fig. 6 normally in radial and axial feed, about 1½ to 3 tooth-pitches do the work, whereas in diagonal hobbing more number of teeth are in operation. Accuracy of the gear produced b diagonal hobbing depends on the accuracy of the hob over the number of teeth, and its pressed over number of teeth. As in radial and axial feed only a limited number of teeth do the actual cutting, the wear of they hob will be concentrated only on these few teeth. In order to spread this wear over all the teeth of the hob, many machines are fitted with automatic hob shift.
3 comments:
gear shaper cutters
Tool Masters is the leading innovator and manufacturer of a wide range of precison Cutting Tools.Our product quality and range is well supported by 'State-of-the-art' machines for manufacture with a strict in-process control.
Radial feed is used where there is restriction to axial motion, for example, in cutting distributor gear on cam shaft, where there is obstruction on both sides of the gear.gear cutters
Thanks for sharing this great information about hob cutters.
Gear Hobs Manufacturers
Post a Comment