Source: https://guthlabs.ai/docs/instruments/bolt-torque-to-preload-calculator/

instrument / verified-with-binding-errata

# Bolt Torque-to-Preload Calculator

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

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **verified-with-binding-errata**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/bolt-torque-to-preload-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/bolt-torque-to-preload-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/bolt-torque-to-preload-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/bolt-torque-to-preload-calculator/qualification/>)

## 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

**torque(_converted)** · vector 2

4572 N·mm / 4.572 N·m

45720 N·mm / 45.72 N·m

0.18×12.7×20000 dropped a zero; her v3 imperial case exact

## 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`