Shaft & Key Calculator (ISO 6885)

Purpose

The calculator solves two classic mechanical engineering tasks:

1. Solid shaft diameter calculation from the torsional strength condition.
2. Parallel key selection (section b × h, groove depths t1/t2, length l) from bearing (crushing) and shear conditions with a subsequent l ≤ 1.5·d check.

Input is just torque T [N·m] and material. Allowable stresses are filled in automatically but can be overridden manually.

Features

• Shaft diameter calculation using the mechanics of materials formula
• Rounding of the diameter up to the nearest value of the Ra40 standard series (GOST 6636)
• Automatic key section selection per ISO 6885 (shaft-diameter-dependent table)
• Required key length calculation by two criteria:
  • bearing / crushing (working height k = h - t1)
  • shear (width b)
• Selection of the larger of the two values and rounding to the standard length series (per ISO 3)
• Validation of l ≤ 1.5·d with a recommendation (two keys / splined connection) on failure
• Interactive specified length check — slider 10–300 mm with live calculation:
  • actual stresses σ and τ vs allowable
  • status OK ✓ / FAILED ✗
  • progress bars and utilization percentage for each criterion
• Material selection with auto-filled allowable stresses + manual override checkbox

GitHub