Bolt Torque-to-Preload Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

Area

Mechanical, Civil & Structural Engineering — Statics/Dynamics, Strength of Materials, Machine Design, Civil, HVAC, Vibration

Tranche

tranche-5

Evidence ID

t5-031

Ledger rows

1

No ledger note is attached.

Review findings

The forward formula is acceptable as an estimate, and the supplied honest-label warning is appropriate. Final approval requires explicit unit handling, defined reverse-operation behavior, input validation, and clarification of the K-factor table and its applicability.

Formula and scope findings

• T = K·d·F is the standard empirical nut-factor approximation for torque required to achieve preload; it is not a deterministic physical law.
• The stated specification claims operation in both directions, but only the forward formula and torque output are explicitly defined. The inverse formulas F = T/(K·d) and K = T/(d·F) must be specified if reverse calculation is supported.
• K = 0.2 must not be treated as a universal steel value; the nut factor depends strongly on lubrication, finish, threads, washers, and installation conditions.

Unit assumptions

• d, F, and T must use a consistent unit system: for example, d in metres and F in newtons produce T in newton-metres; d in millimetres and F in newtons produce T in newton-millimetres.
• K is dimensionless.
• The specification does not state accepted input units or whether automatic unit conversion is supported. This is an exact ambiguity requiring review.
• The stated typical K-factor range and table entries need defined conditions, including bolt and nut finish, lubrication, washer use, thread condition, and whether K values are calibrated for the assembly.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The inverse calculation is undefined when K·d=0 and should reject the input. The result is also highly sensitive to the dry-versus-lubricated K-factor branch and to diameter units; a unit misinterpretation changes 10 N·m to 10000 N·m.

Errata and corrections

Tranche errata

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "bolt_diameter": 0.01,
    "diameter_unit": "m",
    "target_preload": 25000,
    "preload_unit": "N",
    "nut_factor": 0.2
  },
  "expected_outputs": {
    "torque": 50,
    "torque_unit": "N·m"
  },
  "working": "T = K·d·F = 0.20 × 0.010 m × 25,000 N = 0.002 × 25,000 = 50 N·m."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_WITH_ERRATA
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json