Base Tangent Length
Compute span number k and base tangent length W for standard spur gears (involute function invα = tanα − α).
Inputs
Formula
invα = tanα − α; k = ceil(z/9); W = m·cosα·((k−0.5)π + z·invα)
How to use
- Fill in Teeth z, Module m, Pressure angle α in the Inputs section (watch the unit on each field).
- Click Calculate; the tool evaluates the formula shown above.
- Read Span k, Base tangent W, Involute invα in the results area.
Formula notesBase tangent length W_k = m·[(k−0.5)·cosα + z·invα], invα = tanα − α; k = span tooth count.