Straight gear can also be called spur gear. Straight gear is gear that its simple construction form like cylinder that doesn’t too thin or has certain thick measurement. One of the straight gear profit it easy in its making process. 
Straight gear transmit rotate movement from one axis to other axis. The axis must be rotated with the same speed or the opposite, the same direction or the opposite. But it must have the same module. Usually this gear is used to transmit the power in the circle of two axis that it has parallel position. In general gear theory there is belief that gear is rigid work piece that almost doesn’t change its form for long time. In making straight gear has parameters that must be indeed, for example that has relation with its size that showed in the picture below:
Straight gear terminology
Information:
Dt = Diameter tusuk ( Stick Diameter) = z x m
Dk = Diameter kepala (Head Diameter) = Dt + 2m
Dr = Diameter dasar (Base Diameter) = Dt – 2 Hg
Ha = Tinggi kepala gigi (High of teeth Head) = 1 x m
Hi = Tinggi kaki gigi (High of teeth leg) = 1,25 x m
Z = Jumlah gigi ( Teeth Quantity)
Hg = Dalam gigi ( Inside the teeth) = 2,25 x m
P = Tusuk gigi (pitch) = p x m
Tg = Tebal gigi ( Teeth thick) = 1,5708 x m
b = Lebar gigi ( Teeth wide ) = 0,75 x m
Making Process
1. In Hobbing machine
In ATMI we can find this making process in the Pfauter machine. The work piece that is still in the solid position will be sliced by hobbing cutter. The main requisite cutter that used must has the same module as the work piece that will make.
2. In milling machine
Process in this machine is done manually. We must use additional tool that is dividing head for define the amount of teeth in the work piece that will be make with the mediator gear ratio that is arranged certainty can get gear that suitable for work piece that will make cutter module that is turned in spindle
3. Gear Cutting machine
The process in this machine use hydraulic system. Cutter move up and down with the measurement that has been set, slice the work piece that the circle has been set step by step.
This three gear making process will not fluent if do not use oil. Oil has function as the cooling liquid, slippery so that there will be slip and durable the cutter until it can be used in the long time.
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