Design calculators

First-pass sanity checks for the rules the selector flags. Representative rules of thumb: verify against MMPDS, the OEM process spec, and your stress group before release.

Grip length planner →

Enter each zone's design grip ± tolerance (or stack min/max) and get the covering dash numbers plus a buy list with margin.

Your quote →

Collect lines from anywhere on the site into one spec-complete request with certs, need-by and tooling. SpecLok sources it from authorized distributors and returns price, lead time and certs.

BOM decoder →

Paste a fastener BOM and get every line identified, plus the unidentifiable lines, proprietary-tooling families, and long-lead items.

Part-number cross-reference →

One part number in: its sourced NAS, MS, AN and manufacturer equivalents, each with its document, and the install tooling each one needs.

Installation tooling guide →

What it takes to install each family properly: tool class, proprietary or standard, training burden, and inspection, for all 20 families.

Edge distance & pitch

Minimum hole-to-edge and hole-to-hole spacing from the fastener diameter.

Metal edge distance (2D)0.5"

Source: FAA AC 43.13-1B para 4-57c(1): edge distance not less than 2D (single-row rivets); NASA RP-1228 p.21: nominal 2D.

Metal pitch, single row (3D min)0.75"

Source: FAA AC 43.13-1B para 4-57c(1): spacing not less than 3D (single row).

Metal pitch, double row (4D)1"

Source: FAA AC 43.13-1B Fig. 4-5: double row, 4D pitch and 4D between rows.

Composite edge, load direction (3.0D)0.75"
Composite side distance (2.5D + 0.06)0.685"

Source: MIL-HDBK-17-3F Vol. 3 §12.3.1.2, C-23: 3.0D edge distance in the direction of major load; 2.5D + 0.06 side distance.

Composite spacing, intermediate rows (4D)1"

Source: MIL-HDBK-17-3F Vol. 3 §12.3.1.2, C-11: w/d = 4 for intermediate fasteners (5 at the first row, 3 at the last).

Bearing stress check

Bearing stress = ultimate load / (diameter × thickness), vs the MIL-HDBK-5J ultimate bearing allowable (Fbru) at e/D = 2.0. Compare limit load against Fbry.

Within allowable40 ksi
Fbru 129 ksi · Fbry 88 ksimargin +223%

Source: Allowable: MIL-HDBK-5J Table 3.2.3.0(b1), 2024-T3 bare sheet 0.010-0.128 in, A-basis, e/D = 2.0 (dry pin). Bearing stress = P / (D·t). Allowables: MIL-HDBK-5J Fbru / Fbry at e/D = 2.0 (dry pin), see the material row.

Composite bearing allowables depend on the laminate and are not published generically: use your program's CMH-17 or test data.

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