OEM Custom Stainless Steel Flange Bolts
Welle Fasteners is a China-based OEM supplier of custom stainless steel flange bolts and other precision fasteners. We support drawing-based production in A2, A4, 304, 316 and other specified stainless steel grades, with manufacturing processes including cold heading, thread rolling, CNC machining and secondary finishing.
Common configurations include:
- Plain flange bolts for general clamping applications
- Serrated flange bolts where additional resistance to rotation is required
- Fully threaded flange bolts for applications with limited grip length
- Partially threaded versions where the unthreaded shank is required
- Metric flange bolts manufactured to a specified dimensional standard
- Custom Stainless Steel Flange Bolt designs produced from drawings
How Are Flange Bolts Different from Standard Hex Bolts?
The main difference is the integrated bearing flange.
A conventional hex bolt normally has a relatively small bearing surface under its head and may require a separate washer to distribute the load. A Hex Flange Bolt incorporates this bearing surface into the bolt itself.
Feature | Standard Hex Bolt | Stainless Steel Flange Bolt |
Head | Hexagonal | Hexagonal with integrated flange |
Bearing area | Smaller | Larger |
Separate washer | Often required | May not be required |
Assembly | Bolt + washer when specified | Single fastener component |
Flange surface | None | Plain or serrated |
Customization | Standard and custom | Standard and custom |
This distinction is important when selecting a hex flange head bolt for automated assembly or equipment where installation time, component count and consistent bearing contact matter.
A serrated flange should also be selected carefully. Its teeth can increase resistance to loosening by creating mechanical interference with the mating surface, but they may leave marks on painted, coated or finished surfaces. For applications where surface protection is important, a plain flange is often specified instead.
Types of Stainless Steel Flange Bolts
The classification of a Stainless Steel Flange Bolt should consider more than head shape. Buyers normally need to define the flange configuration, thread form, material and dimensional standard.
Plain and Serrated Flange Bolts
Full-Thread and Partial-Thread Designs
Metric Flange Bolts
Custom Stainless Steel Flange Bolts
A plain flange has a smooth bearing surface. It is suitable when the joint requires load distribution without intentionally damaging the mating surface.
A serrated flange incorporates teeth or serrations beneath the head. These can increase resistance to rotational movement under vibration, but their effectiveness depends on the joint design, preload and mating surface.
A fully threaded bolt has threads extending along most or all of the specified threaded length. This configuration is common where the available grip length is relatively short or where thread engagement along the joint is important.
A partially threaded design has an unthreaded shank between the head and threaded section. The required thread length should be based on the joint geometry rather than selected only from a catalogue.
Metric Flange Bolts are normally specified using the nominal diameter, thread pitch and length, such as M8 × 1.25 × 30 mm.
For international industrial projects, the RFQ should state whether the buyer requires coarse or fine pitch thread, the applicable dimensional standard and the required tolerance.
When a standard flange bolt does not match the assembly, a custom Stainless Steel Flange Bolt can be manufactured according to a drawing or controlled specification. Typical modifications include flange diameter, head dimensions, overall length, thread length, thread pitch, special under-head geometry, marking and surface treatment.
Custom manufacturing is particularly useful when the bolt must interface with an existing housing, bracket, casting, sheet-metal assembly or automated fastening system.
304 and 316 Stainless Steel Flange Bolts
Feature | 304 Stainless Steel Flange Bolts | 316 Stainless Steel Flange Bolts |
Typical ISO fastener grade | A2 | A4 |
Material characteristics | Austenitic stainless steel with good general corrosion resistance | Austenitic stainless steel with higher corrosion resistance due to molybdenum (Mo) |
Corrosion resistance | Good for general industrial and outdoor environments | Better resistance to aggressive and chloride-containing environments |
Chloride resistance | More limited in chloride exposure | Better resistance to chloride-induced pitting and crevice corrosion |
Marine environments | Suitable only for less aggressive conditions | More commonly selected for marine and coastal applications |
Chemical environments | Suitable for many general industrial applications | Better suited to more corrosive chemical environments, depending on the media |
Cost | Generally more economical | Generally more expensive |
Typical applications | Machinery, equipment, general construction, industrial assemblies, and moderate outdoor exposure | Marine equipment, coastal machinery, chemical processing, wastewater equipment, and chloride-exposed applications |
If you wish to purchase stainless steel flange bolts and fasteners, you should prepare:stainless steel grade + property class + dimensional standard + thread specification + required documentation.
Stainless Steel Flange Bolt Standards
There is no single standard that defines every aspect of every Stainless Steel Flange Bolt. The applicable documents should be selected according to the product geometry, thread system, material and market.
ISO 3506-1
ISO 3506-1:2020 is particularly important for corrosion-resistant stainless steel bolts, screws and studs. It defines mechanical and physical properties and covers specified stainless steel grades and property classes. The current edition was reviewed and confirmed in 2025.
ISO 4162
ISO 4162:2012 specifies hexagon bolts with flange in the small series, with metric threads from M5 through M16 and specified product/property combinations including A2-70. It is therefore relevant when the required flange bolt geometry falls within its scope.
ISO 15072
For small-series metric fine-pitch flange bolts, ISO 15072:2012 covers hexagon bolts with flange with metric fine pitch thread from M8 to M16 and includes A2-70 among its specified property classes.
DIN 6921
DIN 6921 is still widely encountered in drawings, supplier catalogues and purchasing specifications for hexagon flange bolts. However, buyers should check the latest applicable product standard or customer specification rather than assuming that an old DIN reference is automatically the governing standard. Some industrial product references now pair or replace DIN 6921 with EN specifications.
ASTM F593
For North American projects, ASTM F593-24 covers stainless steel bolts, hex cap screws and studs in specified alloy groups and conditions. It is particularly relevant when the procurement specification is written around ASTM requirements rather than ISO property classes.
The important point is that a standard should be connected to the actual purchasing requirement. A drawing might define the head and flange geometry, ISO 3506-1 might define stainless steel mechanical requirements, and an additional specification might define surface treatment or documentation.
Stainless Steel Flange Bolt Dimensions and Size Guide
Thread Size | Nominal Length Range | Thread Pitch | Head Width Across Flats (s) | Flange Diameter (dc) |
M5 | 10–50 mm | 0.8 mm | 8 mm | ≈11.8 mm |
M6 | 10–60 mm | 1.0 mm | 10 mm | ≈14.2 mm |
M8 | 12–80 mm | 1.25 mm | 13 mm | ≈17.9 mm |
M10 | 16–100 mm | 1.5 mm | 15 mm | ≈21.8 mm |
M12 | 20–120 mm | 1.75 mm | 18 mm | ≈26.0 mm |
M14 | 25–140 mm | 2.0 mm | 21 mm | ≈29.9 mm |
M16 | 25–160 mm | 2.0 mm | 24 mm | ≈34.5 mm |
M18 | 30–180 mm | 2.5 mm | 27 mm | ≈39.0 mm |
M20 | 35–200 mm | 2.5 mm | 30 mm | ≈42.8 mm |
M22 | 40–220 mm | 2.5 mm | 34 mm | ≈47.3 mm |
M24 | 45–240 mm | 3.0 mm | 36 mm | ≈51.3 mm |
The basic RFQ dimensions normally include:
- Nominal thread diameter
- Thread pitch
- Overall bolt length
- Thread length
- Head height
- Width across flats
- Flange diameter
- Flange thickness or under-head geometry
- Plain or serrated flange
- Dimensional tolerances
For a metric flange bolt, a designation such as M10 × 1.5 × 40 mm identifies the nominal diameter, pitch and length, but it does not necessarily define every head and flange dimension.
When the bolt is intended to replace a standard fastener, referencing the applicable standard can simplify specification. For custom parts, however, a controlled engineering drawing is preferable because the manufacturer needs to know which dimensions are critical.
The effective bolt length should also account for the thickness of the assembled components, washers if used, nut engagement and the required thread projection. Simply selecting a longer bolt does not necessarily improve joint performance.
How Stainless Steel Flange Bolts Are Manufactured?
The manufacturing process for Stainless Steel Flange Bolts depends on the required material, dimensions, applicable standard, production volume, and customization requirements. Standard Metric Flange Bolts are commonly produced through cold forging and thread forming, while custom Stainless Steel Flange Bolts may require CNC machining or additional secondary operations.
Manufacturing Stage | What Happens | Key Quality Considerations |
1. Material Selection | Stainless steel wire or bar stock is selected according to the required specification, such as 304, 316, A2, or A4. | Material grade, chemical composition, material certification, and traceability should match the purchase specification. |
2. Material Preparation | Stainless steel material is cut and prepared into suitable blanks for forming or machining. | Blank dimensions and material condition need to be controlled to support consistent production. |
3. Cold Forging or CNC Machining | Standard Flanged Bolts can be formed by cold forging, while customized designs may require CNC machining or a combination of processes. | Head geometry, flange diameter, bolt length, and other critical dimensions should conform to the approved drawing or standard. |
4. Head and Flange Forming | The hexagonal head and integrated flange are formed to create the Hex Flange Bolt configuration. | Head width, head height, flange diameter, and flange geometry are inspected for dimensional consistency. |
5. Thread Forming or Machining | Threads are produced by thread rolling, cutting, or other suitable processes according to the required specification. | Thread diameter, pitch, tolerance, thread length, and gauge acceptance are critical for proper assembly. |
6. Secondary Operations | Depending on the design, additional operations such as CNC machining, chamfering, deburring, or other customized processes may be performed. | Secondary operations must maintain the dimensional tolerances and functional requirements specified by the buyer. |
7. Surface Treatment | Stainless steel flange bolts may receive cleaning, passivation, or other specified surface treatments when required. | Surface condition, cleanliness, corrosion-resistance requirements, and appearance should be checked according to the order specification. |
8. Dimensional Inspection | Finished Hex Flange Head Bolts are inspected for critical dimensions and tolerances. | Thread dimensions, overall length, head dimensions, flange diameter, and drawing-specific tolerances should be verified. |
9. Mechanical and Material Inspection | Where required, mechanical properties and material characteristics are verified through appropriate testing and documentation. | Requirements may include hardness, tensile properties, chemical composition, and material certificates. |
10. Final Inspection and Packaging | Products are checked for quantity, appearance, identification, packaging, and order conformity before shipment. | Inspection records, labeling, packaging requirements, and traceability should match the buyer’s purchase requirements. |
For OEM projects, the manufacturing process can be adjusted according to the customer’s drawings, samples, specifications, tolerances, material requirements, and production volume. This is particularly important when sourcing custom Stainless Steel Flange Bolts that differ from standard catalog dimensions.
Welle Fasteners supports OEM and drawing-based production of Stainless Steel Flange Bolts, including custom Flanged Bolts, Hex Flange Bolts, Hex Flange Head Bolts, and Metric Flange Bolts. Buyers can provide drawings, material grades, specifications, quantities, and inspection requirements for technical review and quotation.
Stainless Steel Flange Bolt Inspection and Quality Control
Inspection should verify both the fastener’s physical dimensions and its material/mechanical requirements.
A practical quality-control plan can include:
Material verification:
Confirm the stainless steel grade against the purchase specification and material certificate. PMI or chemical analysis may be required for critical applications.
Dimensional inspection:
Check overall length, thread diameter, pitch, head dimensions, flange diameter and other drawing-defined characteristics using calibrated measuring equipment.
Thread inspection:
Use appropriate GO/NO-GO gauges or other specified methods to verify thread conformity.
Mechanical testing:
Depending on the specified grade and property class, tensile strength, proof load and other required mechanical properties should be verified according to the applicable standard.
Surface inspection:
Check for cracks, laps, burrs, forming damage, contamination and other unacceptable surface conditions. ISO 6157-1 establishes limits for various surface discontinuities on bolts, screws and studs within its scope.
Passivation verification:
If passivation is specified, the applicable process and acceptance method should be defined. ASTM A967/A967M-25 provides requirements and test options for chemical passivation treatments of stainless steel parts.
For critical applications, inspection documentation can include material certificates, dimensional reports, mechanical test results, inspection records and lot traceability.
Where Are Stainless Steel Flange Bolts Used?
Stainless steel flange bolts are used where a wider bearing surface and corrosion-resistant fastener are useful.
Typical applications include:
- Industrial machinery
- Automotive and transportation equipment
- Electrical and control equipment
- Outdoor equipment
- Pumps and fluid-handling systems
- Food-processing and sanitary equipment
- Marine and coastal equipment
- Chemical-processing equipment
- General OEM assemblies
The correct grade still depends on the environment. An outdoor assembly does not automatically require A4, while a chloride-rich marine environment may require more careful material selection than a general indoor machine.
For critical joints, engineers should also evaluate preload, friction, thread condition, galling risk and the strength of the mating materials.
What Information Do You Need to Quote Custom Stainless Steel Flange Bolts?
A complete Stainless Steel Flange Bolt RFQ should give the manufacturer enough information to quote the correct product rather than simply provide a catalogue price.
A practical RFQ should include:
RFQ Item | Recommended Information |
Product | Stainless Steel Flange Bolt / Hex Flange Bolt |
Material | A2, A4, 304, 316 or specified grade |
Property class | A2-70, A4-70, A4-80 or required class |
Size | M6, M8, M10, M12, etc. |
Thread | Coarse/fine pitch and tolerance |
Length | Overall length and required tolerance |
Head | Hex head dimensions or standard |
Flange | Diameter, thickness, plain/serrated |
Standard | ISO, ASTM, EN, DIN reference or drawing |
Surface | Plain, passivated or specified finish |
Quantity | Prototype, trial order or annual volume |
Documentation | MTC, inspection report, traceability, etc. |
Application | Environment and service requirements |
For custom parts, the drawing should identify critical dimensions and tolerances. If the bolt is used in a safety-critical assembly, the buyer should also specify the required testing and documentation before production begins.
How to Choose a Stainless Steel Flange Bolt Manufacturer?
Manufacturing Capability
Thread Capability
Dimensional Inspection
For OEM projects, confirm whether the supplier can manufacture custom Stainless Steel Flange Bolts according to 2D drawings, 3D models, samples, or detailed specifications. The manufacturer should also be able to control critical features such as flange diameter, head dimensions, thread configuration, and dimensional tolerances.
Thread quality is critical because a flange bolt must engage correctly with the mating nut or threaded component. When sourcing Metric Flange Bolts, confirm the required thread diameter, pitch, tolerance, thread length, and applicable standard.
For custom Hex Flange Bolts, the manufacturer should be able to produce and inspect threads according to the approved drawing or specification. Thread gauges and other inspection methods can be used to verify dimensional conformity.
This is particularly important for OEM applications where a small thread deviation can affect assembly, torque performance, or interchangeability.
A manufacturer should have a defined inspection process for critical dimensions rather than relying only on visual checks.
Production Volume
Documentation
Engineering Support
When evaluating a Flange Bolts Supplier, consider sample production, trial orders, monthly or annual volume, production lead time, and the supplier’s ability to maintain consistent quality across repeat orders.
For high-volume requirements, it is also useful to confirm whether the manufacturer can maintain the same material, tooling, dimensions, and inspection requirements throughout subsequent production batches.
Depending on the project, buyers may require material certificates, dimensional inspection reports, mechanical test reports, certificates of conformity, packing records, or other quality documents.
If you are purchasing custom Stainless Steel Flange Bolts, provide your documentation requirements when requesting a quotation.
A capable manufacturer should be able to review drawings, identify manufacturing requirements, clarify tolerances, and communicate potential production issues before manufacturing begins.
WelleFasteners supports OEM and drawing-based production of custom Stainless Steel Flange Bolts for industrial buyers. Customers can provide drawings, samples, specifications, required quantities, and inspection requirements for technical review and quotation.
Why Choose Welle Fasteners for Custom Stainless Steel Flange Bolts?
Welle Fasteners focuses on custom stainless steel fasteners for OEM production and industrial supply. Its capabilities include CNC machining, cold forging and thread processing, allowing the manufacturing route to be selected according to the geometry, material, tolerance and production volume.
Welle Fasteners supports custom stainless steel flange bolt projects from drawing review and manufacturing-process selection through production inspection and documentation. Depending on part geometry, material, volume and tolerance requirements, the appropriate combination of cold heading, forgin
For a custom Stainless Steel Flange Bolt, the technical process can begin with a drawing or defined specification covering material, dimensions, thread requirements, flange geometry, surface condition and inspection requirements. This approach is useful when a standard catalogue bolt cannot meet the requirements of an existing assembly.
Welle fastener can support custom bolts, nuts, studs, screws and CNC-machined fasteners for global engineering projects, with attention to dimensional consistency, material requirements and production documentation.
For an RFQ, buyers should provide the drawing or specification, stainless steel grade and property class, dimensions, applicable standard, annual or order quantity and required inspection documents. This gives the manufacturer the information needed to evaluate manufacturability and propose an appropriate production route.
A technically complete specification is ultimately more valuable than simply requesting a “316 stainless flange bolt.” The right Stainless Steel Flange Bolt is the one whose geometry, material, mechanical properties, thread and inspection requirements match the actual joint and service environment.
Can You Manufacture Stainless Steel Flange Bolts According to Drawings?
What Information Is Required for a Custom Flange Bolt Quotation?
Yes. WelleFasteners can manufacture custom stainless steel flange bolts according to customer drawings, specifications, samples, or OEM requirements. For drawing-based production, our engineering team can review key requirements including thread size, bolt length, flange diameter, head dimensions, tolerances, thread specifications, material grade, surface finish, and applicable standards such as DIN or ISO.
For OEM and bulk orders, buyers can provide a 2D/3D drawing, technical specification, sample, or detailed RFQ for evaluation. Welle Instruments can confirm manufacturability, production requirements, and quotation details before moving to sampling or mass production.
To request a quotation for custom stainless steel flange bolts, send us your drawing, material requirement, dimensions, quantity, applicable standard, and delivery requirements. Our team can review your specifications and provide a production and quotation proposal based on your project needs.
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For a drawing-based or OEM quotation, please provide:
- Technical drawing or specification– 2D drawings, 3D CAD files, or detailed dimensions
- Bolt size and dimensions– thread diameter, bolt length, flange diameter, head dimensions, and thread length
- Material– such as 304, 316, A2, or A4 stainless steel
- Fastener property class– such as A2-70 or A4-70 when applicable
- Applicable standard– such as DIN, ISO, or another required specification
- Thread requirements– metric or imperial thread, thread pitch, and thread tolerance
- Surface finish– plain, passivated, or other specified finish
- Required quantity– sample quantity, trial order, or annual/bulk volume
- Packaging requirements– individual packaging, bulk packaging, labeling, or customer-specific requirements
- Delivery requirements– target delivery location and required lead time
If you do not have a complete drawing, you can also provide samples, photographs with dimensions, product specifications, or an existing part number for an initial assessment.
For OEM and bulk orders, Welle Instruments can review your specifications, confirm production requirements, and prepare a quotation based on the required material, dimensions, standards, quantity, and customization level. Send your drawings or RFQ details to discuss custom stainless steel flange bolt production and bulk pricing.
What Inspection Documents Can Be Provided for Custom Stainless Steel Flange Bolts?
How are stainless steel flange bolts inspected?
- Material Test Certificate (MTC)– Provides material grade and chemical composition information for materials such as 304, 316, A2, and A4 stainless steel.
- Dimensional Inspection Report– Records key dimensions such as thread diameter, bolt length, flange diameter, head dimensions, and tolerances.
- Mechanical Test Report– May include tensile strength, yield strength, elongation, and hardness results where applicable.
- Thread Inspection Report– Verifies thread dimensions, pitch, tolerance, and gauge inspection according to the specified standard.
- Surface Inspection Report– Documents visual inspection and surface condition, including scratches, burrs, cracks, and other visible defects.
- Chemical Composition Report– Confirms the chemical composition of the stainless steel when required.
- Certificate of Conformity (CoC)– Confirms that the supplied Flanged Bolt or Hex Flange Bolt meets the agreed specifications and applicable requirements.
- Packing and Quantity Inspection Report– Verifies product quantity, packaging condition, identification, and labeling before shipment.
Inspection normally covers material, dimensions, threads, appearance and mechanical requirements, depending on the application and purchase specification.
Dimensional inspection can include bolt length, head width, head height, flange diameter and other drawing dimensions. Thread inspection checks the nominal diameter, pitch and thread condition, often using suitable gauges. Surface inspection looks for defects such as cracks, burrs, damaged threads or unacceptable surface marks.
For stainless steel fasteners, the material grade may also need to be verified against the purchase specification and material documentation. Where required, mechanical properties, hardness or other tests can be included in the inspection plan. Commercial flange bolt specifications commonly identify both dimensional and material standards, such as DIN 6921 and ASTM fastener specifications.
For custom orders, the inspection criteria should come from the approved drawing, applicable standard and purchase requirements rather than from a generic checklist.
