Gear cutting: Gear cutting is a method of manufacturing gear by removing the excess metal from the gear blank.
Milling machines are used for gear cutting or gear machining as they are capable of cutting every type of gear by using a universal indexing mechanism and a form cutter.
Well in this article, I have explained the complete gear machining by milling.
So let’s dive right into it!
Gear cutting by milling
In gear cutting by milling, the gear blank is first mounted on a mandrel and this mandrel is supported between a dead center and alive center in the indexing head (see above image).
The milling cutter is mounted on the arbor of the milling machine.
The alignment of the milling cutter should be such that the geometric center of the cutter is aligned vertically with the centerline of the indexing head spindle.
The table of the milling machine is moved upward until the gear blank touches the edge of the cutter.
At this stage, the vertical feed dial is set to zero.
Now the table is moved in a horizontal direction until the cutter clears the gear blank.
After this, the table is moved upward by the amount equal to the height or depth of the gear tooth.
If the gear is to be cut in two or more passes, then the vertical movement may be less.
Now the longitudinal feed of the table is engaged and the cutter is rotated.
The gear blank comes in contact with the cutter and hence the metal removal process takes place.
In this way, the gear tooth cutting takes place on the gear blank.
The movement of the table is reversed so that the blank again reaches its original position.
The blank is set for another position (for next tooth cutting).
The procedure is repeated for all the teeth to be made on the periphery of the gear blank.
There are basically two types of gear cutters used in milling;
- Disc type form cutters
- End milling cutters
In disc type flat cutters, the plane of rotation of cutter is radial with respect to the blank.
Disc type form cutters are used in horizontal milling machines.
The end milling cutters (also known as end millers) are the type of cutters that rotate about an axis which is set radially with respect to the blank, and at the same time the cutter travels parallel to the axis of blank.
End milling cutters are used on vertical milling machines.
The end milling cutter can be mounted with the spindle of a vertical milling machine.
Generally the disc form cutters are used to cut big spur gears that possess larger pitch. While the end milling cutter is used to manufacture pinion of a larger pitch.
Advantages of cutting gears by milling
The advantages of gear machining by milling method are mentioned below.
- By milling, all types of gears like spur gear, helical gear, worm gear, as well as bevel gears can be manufactured.
- Gear machining can be done by conventional milling machines available in a workshop.
- Initial cost of gear cutters is very less as compared to cutters used in gear hobbing or gear shaping process.
- For manufacturing of small quantities of gears, the gear milling method is very economical.
Disadvantages of cutting gears by milling
The disadvantages of gear machining by milling method are mentioned below.
- The milling technique for gear cutting is a slow method, as it cuts only one tooth at a time. Because of this, the production rate is slow.
- The accuracy of the gear pitch depends on the accuracy of the indexing device. But the major problem is that the indexing device is not very precise.
- Gear tooth profile depends on the accuracy of the cutter profile.
- Also by using this method, the internal teeth can not be cut.