{
  "title": "Torque Specification Database",
  "author": "Chamnan Vu",
  "version": "1.0",
  "standard": "SAE J429",
  "lastUpdated": "2026-07-18",
  "grades": {
    "grade5": {
      "name": "SAE Grade 5",
      "material": "Medium Carbon Steel",
      "markings": "Three radial dashes",
      "tensileStrengthPsi": 120000,
      "yieldStrengthPsi": 92000,
      "hardnessRc": "32-38",
      "stressAreaFormula": "π × ((d_minor + d_mean)/2)² / 4",
      "referenceUrl": "https://en.wikipedia.org/wiki/Metric_bolt_strength_classes"
    },
    "grade8": {
      "name": "SAE Grade 8",
      "material": "Quenched & Tempered Alloy Steel",
      "markings": "Six radial dashes",
      "tensileStrengthPsi": 150000,
      "yieldStrengthPsi": 130000,
      "hardnessRc": "33-39",
      "stressAreaFormula": "π × ((d_minor + d_mean)/2)² / 4",
      "referenceUrl": "https://en.wikipedia.org/wiki/Metric_bolt_strength_classes"
    },
    "metric10_9": {
      "name": "ISO Metric 10.9",
      "material": "Alloy Steel, Heat Treated",
      "markings": "10.9",
      "tensileStrengthPsi": 180000,
      "yieldStrengthPsi": 153000,
      "hardnessRc": "32-38",
      "stressAreaFormula": "π × ((d_minor + d_mean)/2)² / 4",
      "referenceUrl": "https://en.wikipedia.org/wiki/Metric_bolt_strength_classes"
    },
    "metric12_9": {
      "name": "ISO Metric 12.9",
      "material": "High-Strength Alloy Steel",
      "markings": "12.9",
      "tensileStrengthPsi": 210000,
      "yieldStrengthPsi": 178000,
      "hardnessRc": "36-42",
      "stressAreaFormula": "π × ((d_minor + d_mean)/2)² / 4",
      "referenceUrl": "https://en.wikipedia.org/wiki/Metric_bolt_strength_classes"
    }
  },
  "lubricationCoefficients": {
    "dry": { "mu": 0.15, "description": "Unlubricated threads" },
    "oiled": { "mu": 0.12, "description": "Light oil coating" },
    "wax": { "mu": 0.08, "description": "Wax or grease treatment" }
  },
  "verificationProtocol": [
    "Clean threads (remove rust, debris)",
    "Apply lubrication evenly",
    "Tighten in STAR PATTERN",
    "Three passes: 30%, 60%, 100%",
    "Mark with torque seal"
  ],
  "formula": {
    "preloadTarget": "0.75 × YieldStrength × StressArea",
    "torqueEquation": "T = K × D × F",
    "variables": {
      "T": "Target torque (ft-lbs)",
      "K": "Torque coefficient (≈ friction factor μ)",
      "D": "Nominal diameter (inches)",
      "F": "Target preload (lbs)"
    }
  },
  "citations": [
    {
      "source": "SAE J429 Standard",
      "url": "https://en.wikipedia.org/wiki/Metric_bolt_strength_classes"
    },
    {
      "source": "ASTM F3125 High-Strength Bolts",
      "url": "https://web.archive.org/web/2023/*"
    },
    {
      "source": "ASME B18.2.6.1M Thread Dimensions",
      "url": "https://asme.org/"
    }
  ]
}