Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
A286 Shoulder Bolts
A286 shoulder bolts (also called stripper bolts, shoulder screws, pivot bolts, stand-off bolts) feature a precision unthreaded cylindrical shoulder between the head and the threaded end, used as a pivot, guide pin, or precision spacer. TorqBolt manufactures A286 shoulder bolts to ASME B18.3 (US inch series), ISO 7379 (metric), and NAS 1352 (aerospace) standards in 1/4"-1" and M5-M30 sizes. Heat-treated to ASTM A453 grade 660 Class A for 130 ksi tensile, 95 ksi yield. Shoulder diameter ground to h7 / h8 tolerance (typ. ±0.01-0.02 mm) for precision sliding fit; hex socket drive on cylindrical or hex head. See parent A286 bolts, related socket head cap screws, dowel pins (alternative precision-fit fastener), and the canonical chemical composition + mechanical properties pages.
About A286 Shoulder Bolts
TorqBolt produces A286 shoulder bolts in three primary configurations: standard hex-head shoulder (ASME B18.3, hex external drive), socket-head shoulder (cylindrical head, internal hex drive, most common), and aerospace shoulder (NAS 1352, MIL-S-8879 thread, AS9100D AQMS). The unthreaded shoulder ⌀ is precision-ground after solution treatment to h7 (±0.012 mm at ⌀ 10 mm) for sliding-fit pivot applications, or h8 (±0.022 mm) for general guide-pin applications. Threaded end is rolled (not cut) to Class 6g / 3A. Each shoulder bolt undergoes 100 % shoulder ⌀ snap-gauge inspection, out-of-tolerance shoulders cause assembly mis-fit at the field. Material is solution-treated 1650 °F + aged 1325 °F per AMS 5737 / ASTM A453 Class A.
A286 Shoulder Bolt Configurations
TorqBolt produces shoulder bolts in five primary configurations, pick by drive style and dimensional standard:
- Socket head shoulder bolt (ASME B18.3), Cylindrical head with internal hex drive. Shoulder ⌀ = nominal, threaded shank 1 size smaller (e.g. shoulder 1/4 inch → 10-32 UNF thread). Most common configuration.
- Hex head shoulder bolt, External hex drive, used where Allen-key access is unavailable or torque values are high enough to prefer external wrench.
- Aerospace NAS 1352 shoulder bolt, Per NAS 1352 dimensional spec, MIL-S-8879 thread, AS9100D quality, magnetic permeability < 1.005. The standard CRES A286 pivot bolt for aircraft engine and structure.
- ISO 7379 stripper bolt (metric), European metric equivalent of ASME B18.3. Used in Europe and on metric drawings, same shoulder/thread relationship, hex socket drive.
- Stripper bolt with snap-ring groove, Custom variant: ASME B18.3 shoulder with circumferential groove on shank for retaining-ring captivation. Used in stripper / press-tool die-set guidance.
A286 Shoulder Bolt Sizes & Tolerance Reference
| Shoulder ⌀ | Thread | Shoulder length | Head ⌀ | Hex socket | Tolerance |
|---|---|---|---|---|---|
| 1/4 (6.35 mm) | 10-32 UNF | 5/16 - 4 inch | 0.375 inch | 1/8 inch | h7 ±0.012 |
| 5/16 (7.94 mm) | 1/4-28 UNF | 3/8 - 4 inch | 0.4375 inch | 5/32 inch | h7 ±0.012 |
| 3/8 (9.53 mm) | 5/16-24 UNF | 1/2 - 4 inch | 0.5625 inch | 3/16 inch | h7 ±0.015 |
| 1/2 (12.7 mm) | 3/8-24 UNF | 5/8 - 4 inch | 0.75 inch | 1/4 inch | h7 ±0.015 |
| M6 | M5 × 0.8 | 8-50 mm | 10 mm | 3 mm | h8 ±0.018 |
| M8 | M6 × 1.0 | 10-60 mm | 13 mm | 4 mm | h8 ±0.022 |
| M10 | M8 × 1.25 | 12-80 mm | 16 mm | 5 mm | h8 ±0.022 |
| M12 | M10 × 1.5 | 16-100 mm | 18 mm | 6 mm | h8 ±0.027 |
A286 Shoulder Bolts Manufacturing Process
Every a286 shoulder bolts TorqBolt ships traces back to a vacuum-induction-melted plus vacuum-arc-remelted (VIM-VAR) ingot meeting AMS 5731 / 5732 chemistry. The complete process route:
- Bar prep + turning: AMS 5731 bar turned to oversize shoulder ⌀ + thread blank diameter. Sizes ≤ 1/2 inch from cold-drawn bar; sizes > 1/2 inch from hot-rolled.
- Head forming: Cylindrical head cold-headed (sizes ≤ M16) or 5-axis machined (M20+). Hex socket forged or broached per ASME B18.3 / ISO 4762 socket dimensions.
- Thread rolling: Threaded end rolled (not cut), Class 6g metric / 3A inch. Aerospace lots use MIL-S-8879 Class 3.
- Solution treatment: Vacuum heat-treat 1650 °F (899 °C, AMS 5737 / ASTM A453 Cl. A) for 1 hour, oil-quench.
- Precipitation aging: 1325 °F (718 °C) for 16 hours, air-cool. Hardness 277-302 HBW post-aging.
- Shoulder grinding: Critical step, shoulder ⌀ ground after aging to h7 (sizes < 1/2 inch) or h8 (sizes ≥ M16) tolerance using cylindrical grinder. Surface roughness Ra ≤ 0.4 µm.
- Passivation: Pickle in HNO₃ + HF, water rinse, passivate per ASTM A967 Type II to remove free iron from grinding.
- Inspection: 100 % shoulder ⌀ snap-gauge, every shoulder bolt verified within tolerance before pack.
- Marking & pack: Head-stamped 'A286' + lot + manufacturer 'TB'. Vacuum-bagged with desiccant for corrosion protection.
A286 Shoulder Bolts Inspection & Certification
Each lot ships with a signed inspection certificate. Aerospace lots default to AS9102 FAI reporting under our AS9100D AQMS coverage. Industrial orders default to EN 10204 type 3.1; sour-service and offshore step up to type 3.2 with third-party witness.
- 100 % shoulder ⌀ snap-gauge per drawing tolerance, h7 or h8, every shoulder bolt.
- 100 % shoulder length micrometer check, tolerance ±0.10 mm (commercial), ±0.05 mm (aerospace).
- 100 % thread-gauge GO/NO-GO at the threaded end.
- Hardness traverse 4-point Vickers per heat-treat lot.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace lot.
- Surface roughness Ra ≤ 0.4 µm on shoulder verified with profilometer (sampling).
- AS9102 first-article inspection on aerospace lots per AS9100D.
- Salt-spray ASTM B117 96-hour pass per ASTM A967 for passivated lots.
A286 Shoulder Bolts Torque & Assembly Practice
Shoulder bolts torque to 75 % of room-temperature thread yield, but the threaded section is one size smaller than the shoulder, so the torque limit is set by the SMALLER thread, not the shoulder ⌀. M6 thread torque: 8 N·m oil / 6 N·m anti-seize. M8 thread: 18 N·m oil / 13 N·m anti-seize. M10 thread: 35 N·m oil / 25 N·m anti-seize. The shoulder itself does NOT carry torque, it carries radial bearing load when the joint rotates. Lubricate the threaded end only; keep the shoulder ⌀ free of lubricant to maintain sliding-fit precision.
A286 Shoulder Bolt Applications by Industry
Shoulder bolts serve as precision pivots, guides, and stripper-bolt components. Applications:
- Aerospace control linkage: NAS 1352 shoulder bolts as pivot pins on flight control linkages, hinge points, actuator clevises. Magnetic permeability < 1.005 critical for nav-system isolation.
- Engine accessory mounting: Shoulder bolts as locating pins between accessory gearbox modules, fuel-pump mounting brackets, ground shoulder ⌀ ensures correct module alignment.
- Stamping & press tool: Stripper bolts in progressive-die sets, shoulder guides stripper plate during press cycle, threaded end retains it. Repeated 100,000+ cycle service.
- Industrial machinery: Shoulder bolts as cam follower pivots, lever fulcrum pins, sprocket idler shafts. A286 maintains shoulder ⌀ tolerance at 540-700 °C operation.
- Robotics & automation: Robot joint pivot pins, gripper finger hinges, end-effector linkages. Non-magnetic A286 prevents interference with proximity sensors.
- Medical / instrumentation: Surgical robot joints, MRI-compatible imaging fixtures, particle-accelerator beam alignment pins. Permeability < 1.005 essential.
Governing Standards & Material Specifications
Every A286 fastener is released against the applicable industry standard. EN 10204 type 3.1 mill certificates ship with every order. See the consolidated A286 AMS / ASTM specifications hub for full spec scope.
| Authority | Specification | Coverage |
|---|---|---|
| ASTM | A453 grade 660 Cl. A/B/C/D | High-temperature bolting material |
| ASTM | A638 grade 660 Type 1/2 | Forged bolting stock |
| AMS | 5731 | Bar / forging, solution-treated |
| AMS | 5732 | Bar / forging, solution-treated and aged |
| AMS | 5737 | Bar, solution-treated and aged (precision) |
| UNS | S66286 | Material designation |
| DIN | 1.4980 / X5NiCrTiMoVB25-15-2 | European designation |
| EN | 10204 3.1 / 3.2 | Mill / third-party-witness certification |
| NACE | MR0175 / ISO 15156-3 | Sour-service hardness limit ≤ HRC 35 |
A286 Shoulder Bolts vs Alternative Materials
When selecting a fastener material engineers compare A286 against three alternatives: A286 vs Inconel 718 (top-end performance, 3× cost), A286 vs 17-4 PH (cheaper but limited to 315 °C), and A286 vs Waspaloy (sustained service > 700 °C). Within the 540-700 °C service envelope A286 is the dominant cost-performance choice for non-magnetic, oxidation-resistant bolting. See the consolidated A286 equivalent grades reference for full alloy alternatives.
How to Specify A286 Shoulder Bolts
A complete a286 shoulder bolts callout should include: material spec, heat-treatment condition, dimensional standard, size, thread tolerance class, surface finish, marking, inspection certificate. Example callout:
Shoulder bolt, ASME B18.3, A286 / ASTM A453 grade 660 Class A, ST+A, shoulder 1/4 inch × 1.0 inch length, thread 10-32 UNF, hex socket drive 1/8 inch, head-marked ‘A286’ + lot, h7 shoulder tolerance, EN 10204 3.1.
A286 Shoulder Bolts, Frequently Asked Questions
What is an A286 shoulder bolt?
A precision bolt with three sections: head (hex socket or hex external), unthreaded cylindrical shoulder of nominal ⌀ ground to h7 or h8 tolerance, and threaded end one size smaller than the shoulder. Used as a pivot, guide pin, stripper bolt or precision spacer. Sometimes called shoulder screw, stripper bolt, or pivot bolt.
What is the difference between an A286 shoulder bolt and an A286 hex bolt?
Hex bolt has continuous shank diameter (nominal thread ⌀). Shoulder bolt has an unthreaded shoulder section larger than the threaded end, ground to a precision tolerance (h7 / h8) for sliding-fit pivot or guide-pin function.
What standard governs A286 shoulder bolt dimensions?
ASME B18.3 (US inch series), ISO 7379 (metric), and NAS 1352 (aerospace). All define shoulder ⌀, shoulder length increments, thread size relationship to shoulder, and head dimensions.
What tolerance is the shoulder ⌀ ground to?
h7 (~±0.012 mm at ⌀ 6 mm, ±0.018 mm at ⌀ 25 mm) for precision pivot applications, or h8 (~±0.022 mm at ⌀ 16 mm) for general guide-pin applications. Aerospace NAS 1352 typically specifies h7.
Are A286 shoulder bolts non-magnetic?
Yes, magnetic permeability < 1.005 verified per ASTM A342 on every aerospace lot. Critical for control-linkage pivots near magnetic-flux-sensitive nav and proximity sensors.
Can A286 shoulder bolts replace dowel pins?
Functionally similar (both provide precision-fit alignment), but shoulder bolts also retain the joint via threaded end while dowel pins require press-fit or retaining ring. Use A286 dowel pins for pure alignment without retention; shoulder bolts when alignment + retention required.
What head drive style is most common for A286 shoulder bolts?
Hex socket (internal hex / Allen) drive, accounts for 80 % of shoulder bolt orders. Allows the cylindrical head to be flush or recessed, leaves shoulder ⌀ free of wrench-flat features.
What is the surface finish on the shoulder ⌀?
Ra ≤ 0.4 µm (≤ 16 µin) per ASME B18.3. Achieved by post-aging cylindrical grinding. Aerospace NAS 1352 may specify Ra ≤ 0.2 µm for high-cycle pivot applications.
Are A286 shoulder bolts hardened or aged?
Solution-treated 1650 °F (899 °C) and aged 1325 °F (718 °C) for 16 hours per AMS 5737 / ASTM A453 grade 660 Class A. Final hardness 277-302 HBW (29-32 HRC). Aging done before final shoulder grinding to ensure dimensional stability.
Why TorqBolt for A286 Shoulder Bolts
Three reasons aerospace and gas-turbine OEMs place a286 shoulder bolts orders with us:
- Vertically integrated supply, VIM-VAR melt sourcing from approved AMS-conforming mills, in-house cold heading + thread rolling + vacuum heat-treatment.
- Aerospace AQMS, AS9100D-certified factory in Mumbai with published quality manual covering A286 fastener-specific failure-mode analysis.
- Lead time discipline, 4-6 weeks for ASTM A453 grade 660 standard sizes, 8-12 weeks for custom-drawing aerospace parts.
30+ years of fastener-manufacturing track record. Active certifications cover ISO 9001:2015, AS9100D AQMS, PED 2014/68/EU and NORSOK M-650 QTR.
Recent A286 Shoulder Bolts Order Patterns
Recurring shoulder-bolt applications include aerospace control-linkage pivots (NAS 1352, 1/4 to 5/16 inch), progressive-die stripper bolts on stamping presses (M6 and M10), robot joint hex-head pivots (3/8 to 1/2 inch), and Czech metal-forming line stripper bolts (ISO 7379 M12).
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