Lewei Hardware is a company with 20 years of experience in producing non standard hardware parts and standard fasteners.

Non-standard Flange Bolts — A Solution from Customized Design to Multi-Industry Applications

2026-08-26

In the machinery and automotive industries, flange bolts have become a commonly used fastener thanks to their unique flange design. Compared with ordinary bolts, flange bolts can effectively distribute loads and improve fastening performance. In certain projects, standard flange bolts may not fully meet special application requirements — and that is where non-standard (customized) flange bolts become an important solution.

Standard Flange Bolt

1. Background & Requirements of Non-standard Flange Bolts

In a large-scale machinery and equipment project, standard flange bolts could not fully meet the following requirements:

- High-strength requirements:

The equipment operates under high loads and vibration, placing higher demands on the bolts' tensile strength and fatigue resistance.

- Corrosion resistance:

The equipment is exposed year-round to humid and high-salt-fog environments, so the bolts must possess excellent corrosion resistance.

- Special dimensions:

Due to the equipment's special structure, non-standard lengths, diameters, and a unique flange shape were required.

Non-standard Flange Bolts — A Solution from Customized Design to Multi-Industry Applications 2

2. Customized Design of Non-standard Flange Bolts

2.1 Material Selection

Based on project requirements, alloy steel (42CrMo) was selected, with special surface treatment applied.

- High strength: After heat treatment, 42CrMo achieves a tensile strength of up to 1100 MPa with excellent fatigue resistance.

- Corrosion resistance: Galvanizing forms a protective layer that extends the bolt's service life in harsh environments.

2.2 Structural Design Optimization

Non-standard Flange Bolts — A Solution from Customized Design to Multi-Industry Applications 3

The design focus of non-standard flange bolts lies in the flange and the shank:

- Widened flange design:

The flange diameter is larger than the standard size, helping to distribute loads evenly and avoid failure caused by local stress concentration.

- Conical serrated flange face:

Fine conical serrations on the underside of the flange increase friction between the bolt and the mating surface, effectively preventing loosening.

- Special thread length:

Thread length is adjusted according to actual requirements to ensure the bolt fits thick-walled flange connection components.

2.3 Surface Treatment Process

To meet the requirements of highly corrosive environments, the following surface treatments were applied:

- Hot-dip galvanizing:

A thick zinc coating is formed on the bolt surface, significantly improving rust resistance and making it suitable for long-term outdoor use.

- PTFE coating:

A polytetrafluoroethylene coating not only enhances corrosion resistance but also improves thread lubricity, making installation and disassembly easier.

3. Production Process Flow

3.1. Raw material pretreatment:

High-quality alloy steel bars are selected, cut, and initially forged to ensure uniformity of the blank and dimensional accuracy.

3.2. Forging:

The flange and shank are formed in a single hot-forging process, ensuring overall bolt strength and a firm bond between the flange and the shank.

3.3. Thread rolling:

Threads are produced by rolling rather than cutting, avoiding stress concentration and improving thread strength and durability.

3.4. Heat treatment:

Quenching and tempering are applied to achieve the required design strength and toughness.

3.5. Surface treatment:

Galvanizing combined with PTFE coating ensures long-term protective performance in extreme environments.

3.6. Quality inspection:

Dimensional measurement, tensile testing, fatigue testing, and salt-spray testing ensure that every bolt meets the design standard.

4. Application Scenarios & Actual Performance

This non-standard flange bolt has been successfully applied in the following fields:

- Construction machinery and equipment:

Under high-load vibration conditions, the flange bolt provides stable connections and significantly extends equipment service life.

- Offshore platform facilities:

With excellent corrosion resistance, it is suitable for offshore equipment exposed to seawater and salt fog over the long term.

- Heavy vehicle manufacturing:

In heavy trucks and construction vehicles, the high strength of the non-standard flange bolt ensures reliable operation of the chassis and drivetrain. In actual use, this non-standard flange bolt has demonstrated the following advantages:

- Stable connection:

The improved flange design maintains a tight fit under high vibration without frequent maintenance.

- Excellent corrosion resistance:

It retains good appearance and performance even after prolonged exposure to salt-fog environments.

- Extended service life:

The special materials and coating processes effectively reduce bolt replacement frequency and save maintenance costs.

5. Value & Prospects of Non-standard Flange Bolts

Non-standard flange bolts demonstrate advantages that standard parts cannot match in demanding industrial and engineering applications. Through customized design of materials, structure, and processes, this type of fastener can meet a wide range of special requirements and become part of critical components. If your project requires flange bolts with special specifications or performance, non-standard customization is the best choice for achieving reliable connections and long-term performance. Jiangxin Industrial provides professional design and manufacturing services to help make your project a success!

--- About Lewei Hardware

Lewei Hardware is a National High-Tech Enterprise and a Zhejiang Provincial Sci-Tech Enterprise, and a professional fastener manufacturer integrating production, R&D, and sales.

In terms of product supply and demand, non-standard customization accounts for a high proportion of our business — the product specifications involved in non-standard customized production and sales currently exceed 10,000 types.

Business scope:

- Bolts:

Hex head bolts, socket head cap screws, carriage bolts, flange bolts, etc. - Screws:

Machine screws, self-drilling screws, set screws, 12.9-grade shoulder (dowel) screws, hex lag screws, self-tapping screws.

- Nuts:

Hex nuts, K-nuts, nylon insert lock nuts, stamped metal self-locking nuts, hex flange nuts, cap nuts, blind rivet nuts, etc.

- Others: Semi-tubular rivets, step rivets, and custom manufacturing of various non-standard fasteners.