Bolted joint fatigue (dynamic load) strength — fixed M12 geometry
Load-fatigue limit of a bolted joint (M12 thread — fixed, matching the original locked demo) from property class, joint stiffness factor and minimum clamping force.
Fixed to the M12 thread geometry (12 mm: P=1.75mm, d2=10.863mm, d3=9.853mm) exactly as the legacy "please login" demo lock froze it. Unlike its siblings (c3_4, e3_6c) this legacy source has no if/else-if lookup table for other thread sizes at all — the M12 numbers are the only geometry the formula ever computes with, assigned unconditionally after the login gate. Generalizing to other thread sizes here would mean importing a table that is not present in this specific legacy source, so this port is honestly presented as an M12-only reference calculator; property class, joint stiffness factor and minimum clamping force remain fully free inputs, matching what was already variable under the lock.
Method & references
- Load-fatigue limit of a preloaded bolted joint, M12 thread (fixed geometry from the original locked demo — see notes).
The computation is a literal port of the original client-side JavaScript from /calculators/c3_3.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.