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Controlled empirical assembly worksheet

Documented stud torque from target preload

Apply one controlled torque coefficient K to one per-stud target preload P and the matching nominal diameter D. The worksheet performs the empirical arithmetic T = KDP; it does not select a stud, strength, preload, lubricant or assembly procedure.

No material presetsNo generic dry/lubricated KExact SI/imperial unitsNo compliance verdict
Critical boundary: torque is an indirect and friction-sensitive way to target clamp force. A point value of K cannot predict achieved preload or its distribution. Use only data and a procedure matching the exact fastener, nut, bearing surface, coating, lubricant, cleanliness, reuse/cycle condition and tool process.

1. Controlled empirical inputs

Dimensionless point value from the exact controlled configuration; not a generic lubricant label.

Used only for arithmetic preload sensitivity at the nominal torque; it is not a confidence interval unless the source says so.

2. Joint, source and assembly record

3. Confirmations

4. Empirical point result

Nominal torque
Nominal torque
Nominal torque
Normalized target preload

Method and applicability

Tnom = K × D × Pmål
If controlled K bounds are supplied and Tnom is applied: Psens,low = Tnom/(KhighD); Psens,high = Tnom/(KlowD)

What is calculated

  • One empirical nominal torque for one target preload.
  • Exact N, kN, lbf, mm, inch, N·m and lbf conversions.
  • Optional arithmetic K-bound preload sensitivity only.

What must be controlled

  • Target preload from the complete joint design.
  • Configuration-specific K evidence and statistics.
  • Assembly sequence, tool and verification procedure.

What is not calculated

  • Stud strength, stress area, yield/proof utilization or thread stripping.
  • Flange/gasket load distribution, relaxation, thermal or external loads.
  • Achieved-preload probability, acceptance or code compliance.

The optional sensitivity interval is not a guaranteed preload interval and not a statistical confidence/tolerance bound unless the controlled source explicitly defines it that way. A point K by itself provides no scatter estimate.

Sources and standards boundary

  • NASA Goddard — Torque Tension Testing of Fasteners Used for NASA Flight Hardware Applications: gives T = KDP, documents test determination of K, strong dependence on friction/lubrication/configuration and wide scatter; its reported coefficients are specific to tested hardware and are not presets here.
  • NASA RP-1228, Fastener Design Manual, March 1990, printed page 17: presents T = KFd as a quick empirical formula and explicitly warns that an assumed K = 0.2 must not be used blindly.
  • ISO 16047:2005 with Amendment 1:2012: published and confirmed torque/clamp-force test conditions for applicable fasteners; it is a test standard, not a universal K table.
  • ISO 898-1:2013 with Cor 1:2013: published mechanical-property scope for specified carbon/alloy-steel metric fasteners; its official scope explicitly excludes torque/clamp-force performance and points to ISO 16047 for testing.
  • ASME PCC-1—2022: current official scope is pressure-boundary flanged joints with specified ring-type gasket geometry—not every stud application and not a generic K value.
  • VDI 2230 Part 1:2015-11: controlled calculation method for highly stressed single-bolt joints; the licensed method is not reproduced by this point worksheet.
  • ASTM A193/A193M-26: active bolting-material specification for high-temperature/high-pressure and special-purpose applications. It does not justify one universal B7 preload or K value; exact material/design criteria remain controlled project inputs.
  • NIST SP 811 Appendix B: exact inch and pound-force basis used for unit normalization.

Klassifikation: T = KDP is an empirical general-engineering relationship, not an ISO torque formula. The former metric stress-area table, B7/L7/property-class strengths, 70–75% utilization presets, generic dry/oiled/MoS₂/anti-seize coefficients, universal ±25% statement and assembly advice are withheld as NEEDS_LICENSED_SOURCE or exact project-test/procedure data.

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