# GEOM.xls

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### Description

Program to calculate the complete geometry of an involute gear pair, including manufacturing & inspection details. Read the help sheet first

Calculation Reference

Machine Design

To calculate the complete geometry of an involute gear pair, including manufacturing and inspection details, you'll need to determine various parameters such as pitch diameters, base diameters, addendum, dedendum, clearance, tooth thickness, and helix angle (for helical gears). Here's a step-by-step guide:

1. Required input parameters:
• Module (m): The module is the ratio of the pitch diameter to the number of teeth. It should be the same for both gears to ensure proper meshing. The module is typically measured in millimeters per tooth (mm/tooth).
• Number of teeth on gear 1 (N1) and gear 2 (N2)
• Pressure angle (φ): The pressure angle is typically 20° or 14.5° for most gears but can vary based on the application.
• Helix angle (β) (for helical gears): The angle between the helix and an axial line on the gear.
1. Calculate the pitch diameters (D1 and D2): D1 = m * N1 D2 = m * N2

2. Calculate the base diameters (Db1 and Db2): Db1 = D1 * cos(φ) Db2 = D2 * cos(φ)

3. Calculate the addendum (ha) and dedendum (hf): ha = m hf = 1.25 * m

4. Calculate the outside diameters (Do1 and Do2): Do1 = D1 + 2 * ha Do2 = D2 + 2 * ha

5. Calculate the root diameters (Dr1 and Dr2): Dr1 = D1 - 2 * hf Dr2 = D2 - 2 * hf

6. Calculate the clearance (c): c = hf - ha

7. Calculate the tooth thickness at the pitch circle (s1 and s2): s1 = (π * m) / 2 s2 = (π * m) / 2

8. Calculate the center distance (C): C = (D1 + D2) / 2

9. For helical gears, calculate the normal module (mn) and normal pressure angle (φn): mn = m * cos(β) φn = atan(tan(φ) / cos(β))

Now you have the complete geometry of an involute gear pair. To calculate manufacturing and inspection details, you'll need additional parameters such as the tooth form, tolerances, and material properties. The specific calculations for these parameters depend on the gear manufacturing process, gear inspection method, and the desired level of accuracy.

### Calculation Preview

28 Apr 2023
File Size: 50.50 Kb