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 Set Screws
A286 set screws (also called grub screws, socket set screws, headless setscrews) are headless threaded fasteners with a hex socket internal drive — used to lock a shaft in a hub, retain a pulley or sprocket on a shaft, or hold a precision component in axial position. TorqBolt manufactures A286 set screws in four point geometries: flat point (DIN 913 / ISO 4026), cone point (DIN 914 / ISO 4027), dog point (DIN 915 / ISO 4028), and cup point (DIN 916 / ISO 4029) per ASME B18.3 (US) and BS EN ISO 4026-4029 (UK / EU) standards. Sizes M3-M20 metric and #4 to 3/4 inch. Heat-treated to ASTM A453 grade 660 Class A from AMS 5731 bar — 130 ksi tensile, 95 ksi yield. See parent A286 screws, sister SHCS, cap screws, and the canonical chemical composition, heat treatment.
About A286 Set Screws
A286 set screws are headless threaded studs with hex socket drive. Set screws differ from cap screws and bolts in two ways: (1) no head — drive is the internal hex socket only, (2) point geometry on the threaded end is the working surface (flat / cone / cup / dog) — not a head bearing surface. Used in radial-bore applications: shaft set screws, hub-on-shaft retention, collar set screws, machine-tool work-holding, optical-mount alignment, instrumentation pedestal locking. Each set screw is machined or cold-formed from A286 bar (AMS 5731), thread-rolled, point-formed (turning, grinding, or coining), then solution-treated 1650 °F + aged 1325 °F per AMS 5737. Final hardness 277-302 HBW.
A286 Set Screw Point Geometries
Four primary point geometries — selection drives application:
- Flat point (DIN 913 / ISO 4026 / ASME B18.3) — Flat-end set screw — minimal damage to mating surface, low holding force. Used on hardened shaft, frequent re-positioning.
- Cone point (DIN 914 / ISO 4027 / ASME B18.3) — 90° conical end — penetrates mating surface (shaft, collar) for high holding force. Permanent / one-time positioning. Mating shaft typically has matching dimple.
- Cup point (DIN 916 / ISO 4029 / ASME B18.3) — Concave cup-shaped end with sharp peripheral edge — excellent grip on round shafts. Most common general-purpose set screw — 70 % of market.
- Dog point (DIN 915 / ISO 4028 / ASME B18.3) — Reduced-diameter cylindrical projection at the end (1/2 thread diameter) — engages a hole in the mating shaft for positive rotational lock. Used on indexed shaft positioning.
- Knurled cup point (custom) — Cup point with knurled cup perimeter — increased grip on smooth shaft surfaces. Custom-drawing variant.
- Half-dog point (DIN 915 short) — Shorter dog-point projection (1/4 thread diameter) — used in shallow blind holes for limited-engagement positioning.
A286 Set Screw Sizes & Reference
| Metric size | Pitch | Hex socket | Length range | Min. holding torque (N·m) |
|---|---|---|---|---|
| M3 | 0.5 | 1.5 mm | 3-25 mm | 0.5 |
| M4 | 0.7 | 2 mm | 4-30 mm | 1.2 |
| M5 | 0.8 | 2.5 mm | 5-40 mm | 2.5 |
| M6 | 1.0 | 3 mm | 6-50 mm | 5.0 |
| M8 | 1.25 | 4 mm | 8-60 mm | 12 |
| M10 | 1.5 | 5 mm | 10-80 mm | 25 |
| M12 | 1.75 | 6 mm | 12-100 mm | 44 |
| M16 | 2.0 | 8 mm | 16-100 mm | 108 |
| M20 | 2.5 | 10 mm | 20-100 mm | 212 |
A286 Set Screws Manufacturing Process
Every a286 set screws 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 input + cut-to-length: AMS 5731 bar drawn to thread diameter. Bar cut to set-screw blank length.
- Hex socket cold-forming: Hex socket forged in one end of the blank — depth ≈ 0.6 × shank diameter for adequate Allen-key engagement.
- Point geometry machining: Opposite end of blank machined to point geometry: flat (face-grinding), cone (90° tool turning), cup (boring + facing), dog (reduced-⌀ turning).
- Thread rolling: Cylindrical or flat-die thread rolling — Class 6g metric / 2A inch. Rolled threads provide 30-40 % higher fatigue strength.
- Solution treatment: Vacuum heat-treat 1650 °F (899 °C) per AMS 5737 / ASTM A453 Class A. 1 hour per inch, oil-quench.
- Precipitation aging: 1325 °F (718 °C) for 16 hours, air-cool. Hardness 277-302 HBW. Aerospace lots ±5 °C control.
- Point hardness verification (cup point): Cup-point peripheral edge hardness re-checked post-aging — must be ≥ 30 HRC for adequate grip on hardened shaft surfaces.
- Passivation: Pickle + HNO₃ rinse + passivate per ASTM A967 Type II. Optional silver / nickel anti-galling for hardened-shaft applications.
- Marking + bulk pack: Set screws too small for individual marking — lot-marked container, heat traceability label. Bulk pack 100 / 250 / 500 / 1000 pcs.
A286 Set Screws Inspection & Certification
Each lot ships with a signed inspection certificate. Aerospace orders default to AS9100D first-article reporting per AS9102. Industrial orders default to EN 10204 type 3.1. Variant-specific inspection scope:
- 100 % thread-gauge GO/NO-GO per ISO 1502 (commercial) or MIL-S-8879 (aerospace).
- 100 % hex socket dimension per ISO 2936 — across-flats and corner-to-corner.
- Point geometry verified by optical comparator — angle, depth, ⌀ per drawing.
- Length micrometer check — ±0.10 mm tolerance commercial, ±0.05 mm aerospace.
- Hardness traverse 4-point Vickers per heat-treat batch.
- Cup-point edge hardness verified ≥ 30 HRC for grip-critical lots.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace coil.
- AS9102 first-article on aerospace lots; EN 10204 3.1 commercial.
A286 Set Screws Torque & Assembly Practice
Set screws torque to develop holding force on the mating component — typically 50-75 % of yield. Cup-point holding force is 60-70 % of axial load on a 1/4-20 cup point at 100 in-lb torque on a hardened shaft. Cone point: highest holding force but creates dimple in shaft — replacement may require new shaft. Always tighten in 2 stages: 50 % torque + 1/4 turn final to seat the point. For high-vibration applications use thread-locker (Loctite 242 / 263) on the threads. Above 540 °C use nickel anti-seize on threads — galling makes set screw loosen unpredictably.
A286 Set Screw Applications by Industry
Set screws lock components on shafts, pins, and pedestals — applications:
- Aerospace engine accessory shafting: Cup-point set screws lock pulleys, sprockets, and timing wheels on accessory gearbox shafts. Non-magnetic critical for sensor isolation.
- Industrial gas turbines: Cup-point set screws on combustor liner alignment fixtures, exhaust diffuser positioning. A286 gas turbine applications.
- Machine-tool work-holding: Cup-point and dog-point set screws on lathe collets, mill vises, indexing tables — A286 retains hardness at 540 °C process temperatures.
- Robotics & automation: Cone-point set screws on robot joint encoders, motor-shaft couplings, gripper finger positioning. Non-magnetic prevents sensor interference.
- Optical / scientific instrumentation: Flat-point set screws on optical mount alignment screws, mirror positioning, laser-collimator pedestals. Permeability < 1.005 critical.
- Cryogenic LNG & hydrogen: Cup-point set screws on cryogenic valve actuators, hydrogen storage manifold couplings — A286 retains hardness at -196 °C.
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.
| 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 — sol-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 |
A286 Set Screws vs Alternative Materials
Engineers compare A286 against three alternatives: A286 vs Inconel 718, A286 vs 17-4 PH, and A286 vs Waspaloy. A286 wins the 540-700 °C cost-per-MPa-of-retained-preload comparison cleanly. See A286 equivalent grades.
How to Specify A286 Set Screws
A complete a286 set screws callout should include all eight elements: material spec, heat-treatment condition, dimensional standard, size, thread tolerance class, surface finish, marking, inspection certificate. Example callout:
Set screw, ISO 4029 cup point, A286 / UNS S66286, ASTM A453 grade 660 Class A, ST+A, M6 × 1.0 × 12 mm, 6g thread, hex socket 3 mm, EN 10204 3.1.
A286 Set Screws — Frequently Asked Questions
What is a set screw used for?
Set screws lock a shaft inside a hub, pulley, sprocket, or collar — radial-bore application. Also used in optical mount alignment, machine-tool work-holding, robot joint encoder retention. Headless design with hex socket drive permits installation in a tapped through-hole or blind-hole.
Which set screw point geometry should I choose?
Cup point: 70 % of market — best general grip on smooth shaft. Cone point: highest holding force but creates dimple — for permanent installation. Flat point: minimal shaft damage — for hardened shafts and frequent re-positioning. Dog point: positive rotational lock — engages mating hole in shaft for indexed position.
What is the hex key size for an A286 M6 set screw?
3 mm hex key (Allen wrench) per ISO 2936. Note: same hex key as M5 ISO 4762 SHCS but different from M6 SHCS (5 mm hex). Set screws use smaller hex socket than cap screws of the same thread size.
Are A286 set screws magnetic?
No. Magnetic permeability < 1.005 verified on every aerospace lot per ASTM A342. Critical for sensor-isolation on robotic encoders, optical instrumentation, and aerospace shafting.
Can A286 set screws be used with thread-locker?
Yes — Loctite 242 (medium-strength, removable) or 263 (high-strength, permanent) compatible with A286 austenitic surface. Apply 1-2 drops on threads only, finger-tighten, then torque. Above 540 °C thread-locker decomposes — use mechanical thread-form lock or staking instead.
What's the difference between cup point and cone point?
Cup point: concave end with sharp peripheral edge — grips on shaft surface, removable. Cone point: 90° conical end — penetrates and creates dimple in shaft, permanent installation. Cone point requires shaft replacement on removal; cup point allows shaft re-use.
Can A286 set screws hold a shaft against rotation?
Yes. Cup-point holds 60-70 % of axial load on 1/4-20 set screw at 100 in-lb torque (hardened shaft). For positive rotational lock against high torque, use dog-point engaging a matching shaft dimple, or use a Woodruff key + set screw combination.
What's the maximum set screw size?
Standard production: M3 to M20 metric, #4 to 3/4 inch. Larger sizes available custom — M24 to M48, 7/8 inch to 1-1/2 inch — for industrial heavy machinery applications.
Are A286 set screws hardened?
Yes — solution-treated 1650 °F + aged 1325 °F × 16 hours per AMS 5737 / ASTM A453 grade 660 Class A. Final hardness 277-302 HBW (29-32 HRC). Cup-point edge hardness verified ≥ 30 HRC for grip-critical applications.
Why TorqBolt for A286 Set Screws
Three reasons aerospace and gas-turbine OEMs place a286 set screws orders with us:
- Vertically integrated supply — VIM-VAR melt, in-house cold heading + thread rolling + vacuum heat-treatment.
- Aerospace AQMS — AS9100D-certified factory in Mumbai with published quality manual.
- Lead time discipline — 4-6 weeks standard, 8-12 weeks aerospace custom.
30+ years in fastener manufacture; ISO 9001:2015 + AS9100D + PED 2014/68/EU + NORSOK M-650 QTR all current.
Recent A286 Set Screws Order Patterns
Active set-screw applications: ISO 4029 cup-point M6/M8 on aerospace accessory shaft retention, DIN 916 cup-point M5 on robotic joint encoders, DIN 914 cone-point M10 on gas-turbine combustor alignment fixtures, and ASME B18.3 cup-point #6/#8 on optical-mount pedestals.
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