TUMBLER GEAR MECHANISAM
If you see the diagram of tumbler gear mechanism below, E gear is attached to the spindle and known as spindle gear. The purpose of this gear is to rotate feed rod and lead screw in clockwise direction. A and B are tumbler gears and are fitted in a bracket. The lever M placed in the bracket can move upward or downward.
In the construction of the mechanism, gear D is known as stud gear and is connected to lead screw by intermediate gears. It has two different positions. For position 1, the lever M is in upward position and gear A connects with stud gear D and spindle gear E. This arrangement will move carriage towards headstock. On the other hand, if it is in position 2, lever will be in the horizontal position and gear E will connect with gear B, then B to A and A to D. With this arrangement, lead screw direction will reverse and this time, it will move in the anti-clockwise direction and carriage will move towards tailstock.
If we want to give manual feed then lever should be in the middle position which will make sure that the gears are not engaged.
Given below is a photograph of a machine with tumbler gear