JGMA Standard and Specfication

Here is the JGMA specification and tolerance allowance.

AGMA Standard and Specification

Here is the AGMA specification and tolerance allowance :

Gear Types

There are many kinds of gear, below are the common gear we use normally.

Spur Gear
When two spur gears of different sizes mesh together, the larger gear is called a wheel, and the smaller gear is called a pinion. In a simple gear train of two spur gears, the input motion and force are applied to the driver gear. The output motion and force are transmitted by the driven gear. The driver gear rotates the driven gear without slipping.






Bevel Gear
Bevel gears have teeth cut on a cone instead of a cylinder blank. They are used in pairs to transmit rotary motion and torque where the bevel gear shafts are at right angles (90 degrees) to each other.

Worm Gear
A gear which has one toothe is called a worm. The tooth is in the form of a screw thread. A wormwheel meshes with the worm. The wormwheel is a helical gear with teeth inclined so that they can engage with the thread-like worm. The wormwheel transmits torque and rotary motion through a right angle. The worm always drives the wormwheel and never the other way round. Worm mechanisms are very quiet running.

Rack Gear and Pinion Gear
A rack and pinion mechanism is used to transform rotary motion into linear motion and vice versa. A round spur gear, the pinion, meshes with a spur gear which has teeth set in a straight line, the rack.








Internal Gear
Internal gears have better load-carrying capacity than external spur gears. They are safer in use because the teeth are guarded.

Gear Introduction

Gears are the optimal medium for low energy loss, high accuracy and low play, for high-speed machinery such as an automobile transmission.

To understand the gear you have to understand the lever function. The lever and fulcrum make up a simple machine where a stiff beam (the lever) rotates about a fixed pivot (the fulcrum).

The diagram to the right shows a little longer lever. You will notice side "A" is equal to side "B". Or the input force equals the output force. But notice that side "B" is longer than side "A". Therefore the output force will be larger. This is a ratio of output force to input force called mechanical advantage.

The Wheel
Although they may seem very different, wheels and gears are closely related to levers. The wheel is essentially a rotating lever. Think of the diagram of the lever above as being bent into a circle. The center of the circle is the fulcrum. In math we call this the center point.

Wheel "A" is a circle. It is larger than wheel "B". The black circle. You will notice that "A" is larger than "B". The diameter of "A" is larger than "B". If you rotate "B"(the axle) it will move wheel "A". Since "B" is smaller than "A" and moves in a smaller circle than "A" you will use very little input you get a large output. The large ratio of the wheel radius to the axle radius is what makes it easy to turn the wheel at it's rim.