![]() We’ll design and fabricate spur gears using free software (Inkscape) and an online store () that does custom laser cutting at affordable prices out of a variety of materials. This project is adapted from a blog post a student did in my first Mechanisms and Things That Move class at NYU’s ITP. The equations in the table below come from the excellent (and free) design guide published by Boston Gear. It’s not important to understand this parameter, just to know that the pressure angle of all meshing gears must be the same.Īll of these gear parameters relate to each other with simple equations. A pressure angle of 20° is better for small gears, but it doesn’t make much difference. Standard pressure angles are, for some reason, 14.5° and 20°. Pressure Angle: The angle between the line of action (how the contact point between gear teeth travels as they rotate) and the line tangent to the pitch circle.This spacing is critical for creating smooth running gears. Center Distance (C): Half the pitch diameter of the first gear plus half the pitch diameter of the second gear will equal the correct center distance.So, just be careful using outside diameter in your calculations if you estimated it from a gear with an odd number of teeth. ![]() On a gear with an odd number of teeth, if you draw a line from the center of one tooth straight through the center across the gear, the line will fall between two teeth. Note: Gears with an even number of teeth are easiest to measure, since each tooth has another tooth directly across the gear. You can measure this using a caliper like ’s # TOL-00067. Outside Diameter (Do): The biggest circle that touches the edges of the gear teeth.As with diametral pitch, the circular pitch of all meshing gears must be the same. Although rarely used to identify off the shelf gears, you may need this parameter when modeling gears in 2D and 3D software like we’re doing here. This is just pi (Ï€ = 3.14) divided by the diametral pitch (P). Circular Pitch (p) = pi / P: The length of the arc between the center of one tooth and the center of a tooth next to it. ![]() The diametral pitch of all meshing gears must be the same. Common diametral pitches for hobby-size projects are 24, 32, and 48. Think of it as the density of teeth - the higher the number, the smaller and more closely spaced the teeth on a gear.
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