Hi-Lok
Howmet/Huck · Lockbolt / pin-collar
The fatigue-joint default when you can reach both sides — torques itself off.
aka HiLok · Hi Lok · pin and collar
Schematic cross-section, not to scale. Orange = the swaged collar (needs both-side access).
Shear
85–95 ksi
Blind bulb
n/a
Max service
≤ 900°F
Lead-time risk
Low
Diameters
5/32, 3/16, 1/4, 5/16, 3/8"
Head styles
- Protruding
- 100° flush
Standards
- NAS (Hi-Lok series)
- MS
Materials & galvanic compatibility vs CFRP
| Alloy | Shear | vs CFRP | Notes |
|---|---|---|---|
| A286 CRES | 95 ksi | med | — |
| Alloy steel | 95 ksi | med | — |
| Titanium (Ti-6Al-4V) | 95 ksi | low | — |
Install tooling & training
- Tool
- Hex key (holds pin) + collar wrench
- Special / proprietary
- Standard tooling
- Training
- Standard; widely trained.
- Inspection
- Collar break-off confirms torque; protrusion gauge.
Pin held stationary by a hex key while the collar is driven; a frangible wrenching tip shears off at a preset torque — automatic torque-off, no post-install torque inspection.
Sourcing
Lead-time risk: Low
- Peerless Aerospace Fastener ↗
Largest dedicated aerospace fastener inventory; approved source for major OEMs + DoD; multi-year fixed pricing, bonded storage, designated hold-shelf, min/max + safety-stock programs.
- Boeing Distribution (Aviall / KLX) ↗
Formed from Aviall + KLX; broadest catalog coverage for OEM/MRO/airline; deep stock on commodity NAS/MS hardware.
- Incora ↗
Authorized distributor for 60+ manufacturers; AS9100 / EN9120 / FAA AC 00-56; strong vendor-managed-inventory (VMI) and kitting programs.
Need a price or lead time?
Build a spec-complete RFQ and send it to distributors who stock Hi-Lok.
Strengths
- +Automatic torque-off (no torque inspection)
- +Excellent fatigue performance
- +Broadly stocked, standard tooling
Trade-offs
- −Needs access to BOTH sides (not a blind fastener)
- −Galvanic care needed with CFRP — use titanium
Typical applications
- · High-fatigue primary structure (when both sides accessible)
- · Wing, fuselage, empennage joints