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 Hollow Bar
A286 hollow bar is round-cross-section A286 bar with a concentric central bore, produced by trepanning solid round bar or by hot extrusion through a hollow die. Used as raw stock for sleeves, bushings, valve stems with internal porting, and machined components requiring a cylindrical bore eliminating the need for downstream gun-drilling. TorqBolt manufactures A286 hollow bar to AMS 5731 / 5732, ASTM A453 grade 660, and ASTM B637 standards in OD 25-200 mm with ID 10-150 mm. OD : ID ratios from 1.3:1 (thick wall) to 4:1 (thin wall). Heat-treated per AMS 5732 to deliver 130 ksi tensile / 95 ksi yield, retained mechanical properties to 700 °C continuous service. Distinguished from A286 tube/tubing by the heavier wall thickness and primary use as machining stock vs pressure-bearing fluid conveyance. See parent A286 bar stock, sister variants round bar, forged bar, and the canonical chemical composition, heat treatment.
About A286 Hollow Bar
A286 hollow bar is produced by two routes: (1) trepanning, solid hot-rolled round bar bored through with a trepanning tool that removes a central solid core, leaving a hollow tube; and (2) hot extrusion, billet pierced and extruded through a die-and-mandrel set to form hollow stock in a single operation. Trepanning produces hollow bar with smooth, concentric bore and tight OD/ID tolerance; extrusion is more economical for high-volume standard sizes. Wall thickness ratios typically 5-30 mm depending on application. Used for valve stems with internal porting, fluid manifold bodies, hydraulic actuator pistons with internal hydraulic passage, and aerospace shaft assemblies requiring through-bore. Each lot is solution-treated and aged per AMS 5732, surface-pickled and bore-honed if specified, and ships with EN 10204 3.1 mill cert.
A286 Hollow Bar Production Routes
TorqBolt produces A286 hollow bar via three production routes:
- Trepanned hollow bar (precision), Solid hot-rolled bar bored through with a trepanning tool, removes a central solid core, producing concentric ID and tight wall-thickness tolerance. Used for precision sleeves and bushings with critical bore concentricity.
- Extruded hollow bar (high-volume), Billet pierced and extruded through a die-and-mandrel, single-step OD + ID formation. More economical for standard sizes; OD/ID concentricity slightly less than trepanned.
- Centrifugally cast hollow bar (large-section custom), For OD > 150 mm with ID > 75 mm, centrifugal casting provides homogeneous wall thickness and no central porosity. Used for nuclear pressure-vessel cladding sleeves.
- Cold-drawn hollow stock, Hot-extruded hollow stock cold-drawn over a mandrel to tighten OD/ID tolerance and improve surface finish. Used for aerospace precision components.
- Forged hollow bar (heavy section), Open-die forged from ingot, then trepanned. Used for OD 200-300 mm with ID 50-150 mm, the heaviest hollow-bar sizes outside centrifugal casting.
A286 Hollow Bar Sizes & Wall Thickness Reference
| OD × ID | Wall thickness | Production route | OD tolerance | ID tolerance | Available specs |
|---|---|---|---|---|---|
| 25 × 10 mm | 7.5 mm | Trepanned / Extruded | +0.30 / -0 | +0.20 / -0 | AMS 5731 / 5732 |
| 38 × 19 mm | 9.5 mm | Trepanned / Extruded | +0.30 / -0 | +0.30 / -0 | AMS 5731 / 5732 |
| 50 × 25 mm | 12.5 mm | Trepanned / Extruded | +0.40 / -0 | +0.30 / -0 | AMS 5731 / 5732 |
| 75 × 38 mm | 18.5 mm | Trepanned | +0.50 / -0 | +0.40 / -0 | AMS 5731 / 5732 |
| 100 × 50 mm | 25 mm | Trepanned | +0.60 / -0 | +0.50 / -0 | AMS 5731 / 5732 |
| 150 × 75 mm | 37.5 mm | Trepanned / Forged | +1.00 / -0 | +0.80 / -0 | AMS 5731 |
| 200 × 100 mm | 50 mm | Forged + trepanned | +1.50 / -0 | +1.00 / -0 | AMS 5731 / B637 |
A286 Hollow Bar Manufacturing Process
Every a286 hollow bar 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:
- VIM-VAR billet input: AMS 5731 / 5732 chemistry. Aerospace lots double-melted for inclusion control.
- Trepanning route, round bar prep: Hot-rolled solid round bar 1.10 × target OD; sol-treated for trepanning machinability.
- Trepanning operation: CNC trepanning lathe with hollow boring tool, removes a solid core, producing concentric bore. Cooling oil internal flow to prevent tool overheat.
- Extrusion route, billet pre-piercing: Billet hot-pierced through with a punch at 1095 °C, creates initial bore. Billet then heated for extrusion.
- Hot extrusion through die-and-mandrel: Press-extruded at 1095-1150 °C through a die-and-mandrel set, simultaneous OD and ID formation in a single press stroke.
- Cold drawing (precision lots): Extruded hollow stock cold-drawn over a mandrel for tighter OD/ID tolerance and improved surface finish.
- Solution treatment: Vacuum or atmosphere furnace 1650 °F (AMS 5732) or 1800 °F (AMS 5731). 1 h per inch of wall thickness, oil-quench.
- Precipitation aging: 1325 °F for 16 hours, air-cool. Hardness 29-32 HRC.
- Bore honing (precision lots): Internal bore honed for tight ID tolerance and surface finish (Ra ≤ 0.8 µm), optional per drawing.
- Inspection + cut: OD/ID dimensional check, ultrasonic test for sound material, cut to drawing length.
A286 Hollow Bar 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; sour-service and offshore step up to type 3.2 with third-party witness. Inspection scope:
- OD and ID dimensions verified by snap gauge / bore gauge per AMS 5731 / 5732 tolerance.
- Wall-thickness measurement at 4 positions per ASTM A484, concentricity check.
- Surface inspection 100 % visual for laps, seams, mill scale per ASTM E45.
- Ultrasonic inspection per ASTM A388, internal flaw detection for trepanned and forged hollow bar.
- Hardness sample 1 per heat per ASTM E384.
- Tensile coupon from each heat per ASTM E8.
- Magnetic permeability < 1.005 per ASTM A342 on every aerospace heat.
- Bore-finish inspection (Ra ≤ 0.8 µm if honed) verified by profilometer.
- AS9102 first-article on aerospace heats; EN 10204 3.1 commercial.
A286 Hollow Bar Downstream Forming & Machining
Hollow bar is raw stock, torque does not apply directly. Downstream machining and forming: thin-wall hollow bar (wall < 5 mm) is more sensitive to chuck distortion; use soft jaws or 4-jaw self-centering chucks. Pressure-rating of finished hollow components follows ASME PCC-1 / B31.3 calculations using the wall thickness, OD, and A286 yield stress at temperature. For high-pressure hydraulic actuators, design wall thickness for 4× safety factor over working pressure to allow for fatigue cycling.
A286 Hollow Bar Applications by Industry
A286 hollow bar serves machining-stock applications requiring central bore:
- Aerospace valve-stem with internal porting: Hollow bar machined to valve stems with internal hydraulic or pneumatic porting, single-piece design vs gun-drilled solid bar reduces stress concentration.
- Hydraulic actuator pistons: Hollow bar for actuator pistons with internal hydraulic-fluid passage, used in landing-gear, control-surface actuators where fluid passage through the piston is required.
- Aerospace shaft assemblies (through-bore): Hollow bar for jet-engine accessory drive shafts requiring through-bore for fuel or oil passage.
- Industrial valve bodies (high-temperature): Hollow bar machined to high-temperature valve bodies for steam, hot-gas, and chemical-process applications. Eliminates gun-drill operation.
- Bushings & sleeves: Hollow bar as raw stock for high-temperature bushings, sleeves, and bearing housings. Cold-drawn precision hollow stock for tight bore tolerance.
- Cryogenic LNG manifold bodies: Hollow bar for LNG manifold bodies with internal cryogenic-fluid passage. Retains 85 % of room-temperature toughness at -196 °C.
Governing Standards & Material Specifications
Every A286 bar product 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 |
| ASTM | B637 | Precipitation-hardenable bar |
| 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 Hollow Bar vs Alternative Materials
Engineers compare A286 bar against three alternatives: A286 vs Inconel 718, A286 vs 17-4 PH, and A286 vs Waspaloy. See A286 equivalent grades.
How to Specify A286 Hollow Bar
A complete a286 hollow bar callout should include: material spec, heat-treatment condition, dimensional standard, size, surface finish, marking, inspection certificate. Example callout:
A286 hollow bar, AMS 5732, ASTM A453 grade 660 Class A, sol-treated and aged, OD 50.0 mm × ID 25.0 mm × wall 12.5 mm, length 3000 mm, trepanned route, +0.40/-0 OD × +0.30/-0 ID tolerance, EN 10204 3.1.
A286 Hollow Bar, Frequently Asked Questions
What is A286 hollow bar used for?
Hollow bar is round A286 with a concentric central bore, used as raw stock for sleeves, bushings, valve stems with internal porting, hydraulic actuator pistons, and machined components requiring a cylindrical bore. Eliminates downstream gun-drilling operation.
What's the difference between hollow bar and tube?
Hollow bar: heavier wall thickness (typ. 5-50 mm), primary use as machining stock for downstream components. Tube: thinner wall, primary use as fluid-conveyance pipe per ASME B31. A286 tubes are pressure-bearing; hollow bar is raw machining stock.
Trepanned vs extruded hollow bar, which to choose?
Trepanned: tighter OD/ID concentricity, smoother bore, used for precision sleeves and bushings. Extruded: more economical for standard sizes, slightly less concentric. Cold-drawn extruded hollow stock approaches trepanned precision at lower cost.
What's the maximum OD of A286 hollow bar?
Standard production: 200 mm OD via trepanned or forged + trepanned route. Custom: up to 300 mm OD via centrifugal casting. Above 300 mm OD, custom forgings (not bar) are typically specified.
What's the minimum wall thickness?
Trepanned: ~5 mm minimum (limited by trepanning tool diameter). Extruded: ~3 mm minimum. Cold-drawn over mandrel: down to 1 mm wall on small OD. For thin-wall pressure tubing < 3 mm, use A286 tubes/tubing instead.
Is A286 hollow bar ultrasonically inspected?
Yes, 100 % UT per ASTM A388 with straight-beam transducer for trepanned and forged variants. Detects internal flaws around the bore. Aerospace and nuclear lots add Class 1 sensitivity acceptance criteria.
What's the lead time on AMS 5732 hollow bar?
Standard sizes OD 25-100 mm: 6-10 weeks from heat release. Larger sizes 100-200 mm: 10-14 weeks. Custom forged + trepanned > 200 mm: 14-20 weeks. Aerospace AS9102 first-article: add 1-2 weeks.
Can A286 hollow bar be supplied with honed bore?
Yes, internal bore honed to Ra ≤ 0.8 µm (typ. 0.4-0.8 µm) for precision sleeve and bushing applications. Specify on PO; adds 2-3 weeks lead time and ~25 % cost premium.
Is A286 hollow bar magnetic?
No. Magnetic permeability < 1.005 verified per ASTM A342. Preserved through trepanning, extrusion, sol-treatment, and aging. Compatible with non-magnetic instrumentation, MRI, and aerospace electromagnetic-sensitive shaft and bushing assemblies.
Why TorqBolt for A286 Hollow Bar
Three reasons aerospace and gas-turbine OEMs place a286 hollow bar orders with us:
- Vertically integrated supply, VIM-VAR melt sourcing from approved AMS-conforming mills, in-house hot-rolling + cold-drawing + vacuum heat-treatment. No outsourced critical step.
- Aerospace AQMS, AS9100D-certified factory in Mumbai with published quality manual.
- Lead time discipline, 4-6 weeks for ASTM A453 grade 660 standard sizes, 8-12 weeks for custom-drawing aerospace parts.
Over thirty years in fastener manufacture with active ISO 9001:2015, AS9100D, PED, and NORSOK M-650 quality system audits.
Recent A286 Hollow Bar Order Patterns
Active hollow bar orders cover OD 38 × ID 19 mm trepanned for aerospace valve-stem manufacture, OD 75 × ID 38 mm extruded for hydraulic actuator pistons, custom OD 150 × ID 75 mm forged + trepanned for nuclear pressure-vessel cladding sleeves, and AMS 5732 OD 50 × ID 25 mm cold-drawn precision for instrumentation bushings.
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