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BASIC METHOD OF CALCULATING AND DRAWING SPUR GEARS |
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EXAMPLE: DRAWING A SPUR GEAR WITH 15 TEETH, PITCH 22.44mm |
1. Draw the profile of one tooth. Measure the distance across a tooth (see below), along the ‘root’. |
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2. To determine the circumference of the gears circle (root diameter): |
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3. To determine the circumference of the gear’s circle (root diameter) with 15 teeth : |
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4. If drawing the gears by hand, trace the profile with tracing paper and transfer each tooth to the root diameter. If using graphics software, simply copy and paste each ‘tooth’. |
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5. Please note: Because distance ‘A’ is a ‘linear’ measurement (in a straight line) and it is being applied to a circle, you may need to add a couple of mm to the diameter, for all the teeth to fit. To check if this is necessary, draw a circle to the root diameter (112mm in this case) and use a pair of dividers to mark the 15 ‘A’ divisions around the circle. If they are slightly out, draw another circle with a diameter a couple of mm larger, and try with the dividers again. If the ‘A’ measurements fit, carry on to the next stage. |
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6. Use a pair of dividers to mark the profile of the tooth on the tracing paper, onto the root circle. |
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7. Completed spur gear. |
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SET OF EXAMPLES - CALCULATING AND DRAWING SPUR GEARS |
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THE TRUE SHAPE OF SPUR GEARS |
Spur Gears are found in the majority machines, including Lathes and Milling machines. A gear train made up of spur gears allow for the precise, efficient change of speed, which is an essential requirement for accurate machining. |
TYPICAL PROFILE |
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CALCULATIONS FOR TWO MESHING SPUR GEARS 10 TEETH AND TWENTY TEETH |
FOR GEAR 'A' (SEE DIAGRAM OF MESHING GEARS BELOW) |
To determine the circumference of the gear’s circle (root diameter) with 10 teeth : |
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FOR GEAR 'B' (SEE DIAGRAM BELOW) |
To determine the circumference of the gear’s circle (root diameter) with 20 teeth : |
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