curl --request POST \
  --url https://api.iotools.cloud/v1/tool/bolt-torque-calculator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "mode": "grade",
  "thread": "M10",
  "grade": "8.8",
  "preloadPercent": "65",
  "condition": "0.20"
}
'

{
  "tool": "bolt-torque-calculator",
  "tool_version": "1.0.1",
  "outputs": {
    "torque": "43.73 N·m  (32.26 lbf·ft)",
    "torqueTable": [
      {
        "unit": "N·m",
        "value": "43.73"
      },
      {
        "unit": "N·cm",
        "value": "4,373.2"
      },
      {
        "unit": "kgf·m",
        "value": "4.459"
      },
      {
        "unit": "lbf·ft",
        "value": "32.26"
      },
      {
        "unit": "lbf·in",
        "value": "387.1"
      }
    ],
    "preloadUsed": "21,866 N (21.87 kN) — 65% of proof load",
    "boltStress": "377.0 MPa (65% of 580 MPa proof)",
    "notes": "T = K · F · d = 0.20 × 21,866 N × 10 mm.\nK is an empirical constant that swallows thread and under-head friction — it varies with lubrication, coating, washer surface and reuse, so torque control alone typically scatters preload by ±25–30%. Do not substitute this estimate for torque-tension testing on a critical joint."
  },
  "credits_used": 3,
  "credits_remaining": null
}