Non-Standard / Odd-Size Fastener R.F.Q.
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Reference: sales@rrhydraulics.com
Non-Standard & Odd-Size Fasteners
A comprehensive engineering reference and capability overview for procurement engineers, mechanical engineers and maintenance teams requiring fasteners outside standard catalogue ranges — oversized stud bolts for pressure vessels and reactors, extra-long bolts for heat exchangers, non-standard thread forms (ACME, Trapezoidal, Buttress, API), left-hand threads, proprietary equipment replacement fasteners, combination fasteners and custom geometry fasteners in any material grade from carbon steel through exotic alloys.
Non-Standard Fastener Categories
& Engineering Applications
Pressure Vessel · Reactor · Heat Exchanger · Proprietary
When Standard Catalogue Fasteners are Insufficient
Standard metric (ISO 724, DIN 13) and inch UNC/UNF (ASME B1.1) fasteners cover the vast majority of industrial bolted joint requirements. However, a significant range of engineering applications require fasteners that fall outside standard catalogue sizes, thread forms or geometries:
- Large pressure vessels and reactors — high-pressure process vessels (ASME VIII Div.2, API 650/620) may require stud bolts from M80 to M200+ that are far above the standard catalogue range (typically M72 maximum for commercial stud bolts). The large flange diameters and high operating pressures of reactor closures, autoclave covers and large-bore heat exchanger shell-to-channel flanges drive bolt diameters that require custom manufacture.
- Power transmission and lifting equipment — lead screws, jack screws and power transmission threaded rods use ACME (29°), Trapezoidal (30°) or Buttress thread forms designed for efficient power transmission rather than the V-form threads of standard fasteners, which are optimised for joint clamping.
- Proprietary equipment replacement — OEM equipment (pumps, compressors, turbines, valves, pressure vessels) often uses proprietary thread forms, unusual dimensions or non-standard materials that are not available from standard fastener distributors. RR Hydraulics manufactures exact replacements from drawings or from measurements of the original fastener.
- Unusual length requirements — heat exchanger channel and shell flange bolts, reactor nozzle bolts and large valve bonnet studs are often specified at lengths (500–1500 mm) that are far outside the standard bolt length range and must be custom-manufactured.
When enquiring for a non-standard fastener, provide the maximum possible dimensional information: nominal diameter and pitch (e.g. M100×4.0 metric coarse, or 4" UNC 4 TPI); overall length; for stud bolts, the threaded length on each end and the unthreaded shank length; head geometry (across-flats size, head height, drive type); material grade (ASTM or EN designation); thread class (6g/6H for metric, 2A/2B for inch); surface finish or coating; and quantity. The more complete the specification, the faster and more accurate the quotation. Attaching a dimensioned drawing (DXF, DWG, PDF or even a hand-drawn sketch with dimensions) eliminates ambiguity entirely and is strongly recommended for complex items.
Non-Standard Fastener Categories — Engineering Descriptions
Thread Form Reference, Odd Sizes
& Specification Data
Metric Coarse/Fine · UNC / UNF · Left-Hand · Large Pitch
| Thread Form | Standard | Angle | Profile | Primary Application | Available from RR Hydraulics |
|---|---|---|---|---|---|
| ISO Metric Coarse | ISO 724 / DIN 13 | 60° | V-thread, flat crest/root | General fastening — standard catalogue | Stock — M4 to M72 |
| ISO Metric Fine (MF) | ISO 724 / DIN 13 | 60° | V-thread, reduced pitch | Thin-wall sections, high-vibration, precision adj. | Custom — any size/pitch |
| UNC (Unified Coarse) | ASME B1.1 | 60° | V-thread (Unified) | ASME flanges and standard US industrial | Stock — 1/4" to 3" |
| UNF (Unified Fine) | ASME B1.1 | 60° | V-thread, finer pitch | Aerospace, precision assemblies, thin walls | Custom — any size |
| ACME | ASME B1.5 | 29° | Flat crest and root | Power screws, lead screws, jacks, lathes | Custom — any size |
| Trapezoidal (Tr) | ISO 2901 / DIN 103 | 30° | Flat crest and root (metric ACME) | Valve stems, machine tool screws, presses | Custom — any size |
| Buttress | ASME B1.9 | 7°/45° | Asymmetric — high load one direction | Breech blocks, drill collars, quick-connect closures | Custom — any size |
| API Buttress (Casing) | API 5B | 3°/10° | Tapered buttress (oil country) | Oil/gas casing, tubing, drill string connections | Custom — per API 5B |
| Whitworth (BSW) | BS 84 / ISO 228 | 55° | Rounded crest and root | Legacy British industrial, pipe fittings | Custom — any size |
| BSPT (Tapered Pipe) | ISO 7-1 / BS 21 | 55° | Tapered Whitworth form | Pipe thread sealing connections | Stock and custom |
| Left-Hand Metric | ISO 724 — LH suffix | 60° | Opposite helix to standard | Rotating equipment, safety, turnbuckles | Custom — any size |
| Left-Hand UNC | ASME B1.1 — LH | 60° | Opposite helix to standard | As above, inch series | Custom — any size |
| Size Range | Thread | Typical Application | Standard Material | Typical Lead Time |
|---|---|---|---|---|
| M80×6 to M100×6 | ISO metric coarse | Large pressure vessel flanges, reactor heads | A193 B7 / B7M | 3–5 weeks |
| M100×6 to M130×6 | ISO metric coarse | Autoclave covers, ASME VIII Div.2 vessels | A193 B7 / SS B8M | 4–6 weeks |
| M130×6 to M160×6 | ISO metric coarse | Large reactor nozzles, compressor casings | A193 B7 / Inconel 625 | 5–8 weeks |
| M160×6 to M200+ | ISO metric or custom | Large gate valve bonnets, vessel closures | A193 B7 / custom alloy | 6–12 weeks |
| 4"–6" UNC | ASME B1.1 UNC | US-standard pressure vessel ASME VIII | A193 B7 / B16 | 4–8 weeks |
| 6"–8" UNC | ASME B1.1 UNC | Large reactor closures, ASME Div.2 | A193 B7 / B16 / Inconel | 6–12 weeks |
Lead times are indicative and depend on material availability, order quantity, heat treatment requirements and coating. Exotic alloy (Inconel 625, Hastelloy C276, Duplex 2205) oversized fasteners carry longer lead times due to bar stock availability. Rush orders available at premium — contact sales@rrhydraulics.com with URGENT in the subject line. All oversized stud bolts supplied with EN 10204 3.1/3.2 MTC, dimensional inspection report (OD, thread pitch and class, length), tensile test per ASTM F606 and hardness test per heat as standard documentation.
Materials for Non-Standard Fasteners
& Manufacturing Capabilities
CNC Turning · Thread Rolling · Heat Treatment · NDE
| Material Category | ASTM / EN Grade | Key Properties | Typical Non-Standard Application |
|---|---|---|---|
| CS — Standard | A193 B7 / A194 2H | Yield ≥724 MPa; −29 to +538°C | Large pressure vessel studs; oversized anchor bolts |
| CS — High Temp | A193 B16 (Cr-Mo-V) | High-temp creep resistance to +538°C | Power plant main steam flanges; turbine casing studs |
| CS — LTCS | A320 L7 / L7M | Impact tested at −73°C | Cryogenic vessel large-bore studs; LNG plant |
| Alloy — 2.25Cr-1Mo | A193 B7 / A182 F22 | High-temp H₂ service; creep resistance | Hydrocracker, reformer large-bore studs |
| Alloy — 9Cr-1Mo-V | A193 B7 / A182 F91 | Ultra-high-temp 649°C; creep strength | USC power plant valve bonnet studs |
| SS 316L | A193 B8M Cond.S1 | Corrosion resistant; −196 to +816°C | Chemical plant large-bore custom studs |
| Duplex 2205 | A182 F51 / EN 1.4462 | Yield ≥448 MPa; PREN 34–38 | Offshore sour service large-bore studs |
| Super Duplex 2507 | A182 F53 / EN 1.4410 | Yield ≥550 MPa; PREN 40–43 | Subsea, HPHT, seawater non-standard studs |
| Inconel 625 | B446 N06625 / F468 | Corrosion resistant; −196 to +980°C | Offshore Class 600+ large-bore; acid plant |
| Inconel 718 | B637 N07718 / AMS 5596 | Highest strength Ni alloy; ≥1034 MPa | Wellhead, subsea, HPHT high-strength studs |
| Hastelloy C276 | B574 N10276 / F468 | Excellent HCl, H₂SO₄, wet Cl₂ resistance | FGD, chlorine, acid plant non-standard studs |
| Monel K500 | B865 N05500 / F468 | HF resistance; yield ≥586 MPa aged | HF alkylation unit large studs |
| Titanium Grade 2 / 5 | B348 R50400/R56400 | Seawater/Cl− immune; low density | Desalination, chlorine, subsea custom fasteners |
Manufacturing Capabilities
RR Hydraulics manufactures non-standard and odd-size fasteners on CNC turning centres, thread rolling machines and CNC milling equipment. Key manufacturing capabilities include:
- CNC turning — diameters up to 400 mm OD, lengths up to 3000 mm; tight tolerances (h6 on shaft OD, 6g on thread); surface finish Ra ≤ 1.6 µm as-machined
- Thread rolling — cold thread rolling produces stronger threads than cut threading due to work hardening and compressive residual stresses at thread roots; preferred for high-strength A193 B7 and alloy steel studs; available for M16–M100
- Thread grinding — for precision lead screws, ACME and Trapezoidal threads requiring ±0.005 mm pitch accuracy; available for all thread forms
- Heat treatment — full controlled quench and temper (QT) facility for A193 B7 and alloy steel; solution anneal and age for Inconel 718 and Monel K500; solution anneal for duplex and super duplex
- NDE — ultrasonic testing (UT) for internal defects in large-diameter bar stock; magnetic particle testing (MT) for CS and alloy steel; liquid penetrant testing (PT) for SS and alloy; hardness testing on finished cross-section
How to Order, Documentation
& Quality Requirements
PMI · Tensile Test · Thread Gauge · NDE · TPI
How to Submit a Non-Standard Fastener Enquiry
RR Hydraulics accepts non-standard fastener enquiries in any of the following formats:
- Dimensioned engineering drawing (DXF, DWG, STEP, IGES, PDF or hand-drawn with dimensions) — the fastest and most unambiguous method; attach to email to sales@rrhydraulics.com
- Physical sample with measurement request — send the original fastener by courier; our metrology team will measure all critical dimensions (OD, pitch, thread form, length, head geometry) and confirm the specification before quoting; sample returned with the quotation
- Text specification — provide all the information listed in the callout above (diameter, pitch, length, thread form, material, quantity etc.); our engineers will clarify any ambiguities before quoting
- OEM reference number — if you have the original equipment manufacturer's part number, we can often cross-reference to standard specifications or request the drawing from our supplier network
Applications
Large pressure vessels, autoclaves, reactors and thick-wall heat exchangers in refineries, petrochemical plants and chemical facilities use stud bolts from M80 to M200+ and custom lengths from 400 mm to 1500 mm that are outside standard commercial ranges. These are typically A193 B7 or B16 (high-temperature) for process temperatures up to 538°C, with SS B8M or exotic alloys for corrosive service. Every pressure vessel stud bolt must be accompanied by EN 10204 3.2 MTC, tensile test per ASTM F606, hardness per heat, and dimensional inspection confirming thread class, length and shank diameter.
Steam turbine casing studs, valve bonnet studs, and boiler drum flange studs in power generation plants are often proprietary items specified to the turbine or boiler OEM's drawing. A193 B16 (Cr-Mo-V alloy steel, rated to 538°C) is the standard for steam service above the A193 B7 limit. PWHT (post-weld/post-manufacture heat treatment) and controlled hardness verification are mandatory for B16 and F91 alloy fasteners. These fasteners must also be accompanied by a PWHT certificate and hardness profile across the full cross-section.
Subsea tree, manifold and wellhead connection fasteners in Inconel 625, Inconel 718 and Super Duplex 2507 at sizes from M48 to M100+ require the highest level of quality documentation: EN 10204 3.2 with TPI, 100% PMI, tensile test per ASTM F606, NACE hardness including thread root zone, NACE TM0177 SSC testing, dimensional inspection and thread gauge certificate. Lead times for subsea exotic alloy oversized fasteners are typically 8–16 weeks.
When OEM maintenance parts become unavailable or unaffordable, RR Hydraulics provides exact replacement non-standard fasteners. Our reverse engineering service measures the original fastener to ±0.01 mm accuracy, identifies the material by PMI if unknown, and manufactures replacements with equivalent or superior material specifications. Common replacement items include compressor valve studs, pump bearing housing bolts, heat exchanger tie rods, and reactor head studs from discontinued OEM product lines.
| # | Document | Standard | Requirement |
|---|---|---|---|
| 01 | Material Test Certificate (MTC) | EN 10204 3.1 / 3.2 | 3.2 with TPI for offshore, NACE, pressure vessel, subsea; 3.1 standard otherwise |
| 02 | Dimensional Inspection Report | ISO 1101 / customer drawing | All critical dimensions against drawing: OD, length, threaded lengths, head geometry — mandatory |
| 03 | Thread Gauge Certificate | ASME B1.1 / ISO 965 | Go/No-Go thread gauge per lot; thread class (6g/6H or 2A/2B) confirmed; non-standard thread form gauged to drawing |
| 04 | Tensile Test Report | ASTM F606 / EN ISO 898 | Per heat and diameter; yield, UTS, elongation, reduction of area against ASTM A193 minimums |
| 05 | Hardness Test Report | ASTM E18 / ASTM E10 | Per heat; full cross-section hardness including thread root zone; NACE limits for sour service |
| 06 | PMI Report (XRF / OES) | Project specification | 100% on all SS, duplex, Inconel, exotic alloy and alloy steel fasteners; alloy confirmed by UNS |
| 07 | Heat Treatment Certificate | ASTM A193 / A320 | QT (quench and temper) for B7/B16/alloy; solution anneal for SS/duplex/exotic; PWHT for F11/F22/F91 |
| 08 | NDE Report (UT / MT / PT) | ASTM E114 / E709 / E165 | UT on large-diameter bar stock for internal defects; MT/PT on finished surfaces; mandatory for Class 900+ large-bore |
| 09 | ISPM-15 Phytosanitary Certificate | IPPC / FAO | All wood packing for international export |
RR Hydraulics manufactures and exports non-standard and odd-size fasteners to customer drawings and specifications in all materials — A193 B7/B16, A320 L7, F11/F22/F91, A193 B8M (SS 316L), Duplex 2205, Super Duplex 2507, Inconel 625/718, Hastelloy C276, Monel 400/K500, Titanium Grade 2/5. Oversized stud bolts M80–M200+, extra-long studs up to 1500 mm, ACME/Trapezoidal/Buttress/API thread forms, left-hand threads, combination fasteners and proprietary OEM replacements. EN 10204 3.1/3.2 MTC with TPI, dimensional inspection, thread gauge certificate, ASTM F606 tensile, hardness survey, PMI, heat treatment certificate, UT/MT/PT NDE. Submit your drawing or enquiry to sales@rrhydraulics.com — engineering response within 24–48 hours.