{
  "_schema": "torque_calculator_v1",
  "_author": "augusto-torres",
  "_date": "2026-07-17",
  "_source_standard": "SAE_J1199_friction_coefficient_tests",
  
  "nut_factors": {
    "dry_steel_clean": {
      "k_factor": 0.15,
      "description": "Clean machined surfaces, no lubricant applied",
      "use_case": "Precision aerospace assemblies, laboratory fixtures"
    },
    "zinc_plated_std": {
      "k_factor": 0.18,
      "description": "Hot-dip galvanizing or electroplated zinc coating",
      "use_case": "Automotive fasteners, outdoor structural connections"
    },
    "black_oxide_coating": {
      "k_factor": 0.20,
      "description": "Chemical black oxide conversion coating",
      "use_case": "Industrial tooling bolts, firearm assemblies"
    },
    "as_rolled_carbon": {
      "k_factor": 0.25,
      "description": "Uncoated carbon steel, mill surface finish",
      "use_case": "Heavy construction, temporary bracing"
    },
    "molybdenum_disulfide": {
      "k_factor": 0.10,
      "description": "MoS2 solid lubricant film on threads",
      "use_case": "High-strength aerospace joints, rocket motor casings"
    },
    "ptfe_wax_dry_film": {
      "k_factor": 0.08,
      "description": "PTFE-wax composite dry film lubricant",
      "use_case": "Ultra-high preload applications, cryogenic seals"
    }
  },

  "grade_reference": {
    "iso_8_8": {
      "yield_strength_MPa": 640,
      "ultimate_tensile_MPa": 800,
      "recommended_preload_fraction": 0.75
    },
    "iso_10_9": {
      "yield_strength_MPa": 900,
      "ultimate_tensile_MPa": 1000,
      "recommended_preload_fraction": 0.75
    },
    "iso_12_9": {
      "yield_strength_MPa": 1080,
      "ultimate_tensile_MPa": 1200,
      "recommended_preload_fraction": 0.75
    }
  },

  "conversion_constants": {
    "nm_to_ftlbs": 0.737562,
    "mm_to_m": 0.001,
    "kn_to_n": 1000
  },

  "physics_equation": {
    "form": "T = K × d × F",
    "variables": {
      "T": "Applied torque (Newton-meters)",
      "K": "Nut factor (dimensionless friction coefficient)",
      "d": "Nominal bolt diameter (meters)",
      "F": "Target preload force (Newtons)"
    },
    "derivation_note": "Derived from torsional moment equilibrium at thread interface, accounting for under-head and thread friction components"
  }
}