There are 3 types of gear hobbing according to the direction of feeding the hob.
- Axial hobbing
- Radial hobbing
- Tangential hobbing
Let’s discuss each type of gear hobbing one by one.
#1) Axial hobbing
Axial hobbing is the most common type of hobbing process that is generally used for cutting spur gears as well as helical gears.
In axial type of hobbing, the workpiece (or the gear blank) is brought towards the gear hob so that the desired depth of cut can be achieved.
After this being done, the axial feed is given to the hob which gives a desired cut of teeth on the gear blank.
Axial hobbing can be further classified as conventional hobbing and climb hobbing.
#2) Radial hobbing
As shown in the above image, in radial hobbing, the feed is given to the hob such that it moves radially towards the center of the blank.
This radial feed stops when the hob reaches the full depth of cut.
Radial feeding is suitable for cutting worm wheels having a helix angle of less than 6 or 7 degrees.
During this gear cutting operation, only a small portion of the gear hob performs a cutting operation.
Because of this, the wear of the complete hob is nonuniform.
Hence this may affect the accuracy of the tooth profile of final cut gear.
#3) Tangential hobbing
In tangential hobbing, the gear hob is set at the start of cutting to the full depth of the cut.
After this, it is given a feed in an axial direction.
Tangential hobbing operation is generally used to make worm wheels.
The bottom line
Out of the three types of hobbing, axial hobbing is the most commonly used hobbing process.
But in axial hobbing, there should be enough space for hob approaching length.
If there is not enough space, then the combination of axial and radial feed are preferred.
Gears with excellent rolling properties can be manufactured by combination of radial and tangential feed (which is also known as diagonal feed).
By diagonal feeding, there occurs a uniform wear on the gear hob, which ultimately increases the life of gear hob.