Flange Bolts With Square Nuts

Product introduction

This product is a precision assembly of stainless steel flange bolts and square nuts. The flange bolts come with widened pads to disperse pressure and prevent loosening; the square nuts are square in shape, with a large stress surface and strong torsion resistance. The combination of the two is widely used in vibration equipment, pipe flanges, heavy machinery and photovoltaic mounting systems.

As a typical stainless steel fastener, this combination maintains excellent corrosion resistance in humid, weak acid and alkali environments. When customers require special dimensions (such as non-standard flange diameter, non-standard square nut width across sides), we can provide customization of non-standard fasteners, such as thickening the flange thickness from the standard 2.5mm to 4.0mm, or matching the mixed installation solution of inch threads and metric nuts.

In addition, for occasions where installation space is limited or anti-rotation requirements are extremely high, we can also design special-shaped fasteners, such as flange bolts with positioning bosses or square nuts with anti-slip teeth, to further improve connection reliability.

 

Product design and features

Flange bolt design: There are radial anti-slip teeth under the flange surface, which are embedded in the surface of the connected parts when locking, effectively preventing loosening.

The flange diameter is 15%-20% larger than the standard gasket, eliminating the need for a separate trim washer.

Square nut design: square outer contour, the four corners are evenly stressed and not easy to slip.

The height is usually 10%-15% lower than hex nuts, making them suitable for compact spaces.

Combination advantages: When square nuts are matched with flange bolts, high preload force can be achieved without additional gaskets.

Suitable for quick assembly of pneumatic wrenches, with efficiency increased by more than 30%.

Non-standard and special-shaped capabilities: cold heading non-standard parts can be developed: for example, flange bolts with long guide sections can be formed by cold heading in one step to avoid streamline cutting caused by turning.

For square nuts, special-shaped fasteners can be customized - such as locking square nuts with nylon inserts, or welded square nuts with welding bumps on the bottom.

 

Materials and application areas

Flange bolts: SUS304, SUS316, SUS316L Corrosion resistant, high strength

Square nut: SUS304, SUS316, duplex stainless steel 2205, anti-seize, high temperature resistance

As a professional stainless steel fastener supplier, we can also use cold heading non-standard parts technology to manufacture high-strength A4-80 grade bolts, ensuring a tensile strength of ≥800MPa.

 

Typical application areas:

Petrochemical industry: pipeline flange connection (316 material, anti-chloride corrosion)

Shipbuilding: Deck equipment fixation (requires salt spray resistance of more than 720h)

Food and pharmaceuticals: filling machines, reactors (required to have no dead ends and easy to clean)

New energy: photovoltaic tracking bracket, wind power tower ladder

Heavy machinery: vibrating screen, crusher (requires square nut anti-rotation structure)

If the standard size cannot be met, non-standard fasteners can be provided, such as M20 flange bolts with M20 square nuts but with fine threads (P=1.5mm), which are used in high-vibration-resistant applications.

 

Quality control and certification system

Test items: Dimensional accuracy: flange thickness tolerance ±0.1mm, square nut parallelism ≤0.05mm.

Mechanical properties: guaranteed load, hardness (HV200-280), guaranteed stress test.

Salt spray test: 304 material ≥ 240h, 316 material ≥ 720h (no red rust).

Certification qualifications: ISO 9001:2015 quality management system, IATF 16949 (fasteners for the automotive industry), EU CE + RoHS

For quality control of non-standard and special-shaped parts, the first piece of each batch of special-shaped fasteners is fully inspected, and a three-dimensional coordinate measuring machine is used to verify the complex contours.

For cold heading non-standard parts, cracks and folding defects during the cold heading forming process are monitored throughout the process. Establish a "one item, one code" traceability system to trace traceability from wire to heat treatment records.

 

Customized services

Custom type

Non-standard fasteners, any non-standard length, non-standard flange outer diameter, non-standard square nut dimensions across sides; such as M16×1.5 fine thread flange bolt + 24mm square nut across sides

Special-shaped fasteners, flange surfaces with O-shaped grooves (for sealing rings), square nuts with eccentric holes or bottom chamfers to prevent sticking, stainless steel fasteners, Hastelloy C276, Monel 400 and other special stainless steels; temperature resistance up to 800°C, cold heading non-standard parts, complex stepped shaft bolts, and square nut blanks with flanges formed in one go by a multi-station cold heading machine, which reduces machining costs by 40% compared to machining costs

 

Customization process

Drawings or samples provided → 2. Manufacturability Analysis (DFM) → 3. Free 3D solution confirmation → 4. Sample manufacturing (7-15 days) → 5. Small batch verification → 6. Bulk delivery (15-30 days)

 

FAQ

Q: Can your square nuts be made into non-standard thicknesses? Like half thinner than standard?

A: Yes. We are a professional manufacturer of non-standard fasteners. We can customize square nuts of any thickness, the thinnest can be as thin as 3mm (M6 specification), but the strength requirements need to be confirmed. This type of thin square nut is often used as a special-shaped fastener for internal restraints in electronic equipment.

 

Q: Do flange bolts have to use hexagonal heads? Can it be equipped with inner hexagon or T-shaped head?

A: Absolutely. The flange head can be matched with hexagon socket, plum blossom groove or square drive head. If there are special head shape requirements, cold heading non-standard parts can be designed to avoid secondary processing.

 

Q: What should I do if the stainless steel flange bolts seize after being locked with the square nuts?

A: It is recommended to use different grades of stainless steel (such as 304 for bolts and 316 for nuts), or to wax/molybdenum disulfide the internal threads of the nuts. For high-demand situations, special-shaped fastener square nuts with lubricating grooves can be customized to significantly reduce the probability of seizure.

 

Q: What is the minimum order quantity (MOQ)?

A: The standard specification MOQ is 1,000 sets. For non-standard fasteners or cold-headed non-standard parts, the MOQ is generally 5,000 pieces, but a sample order (100-200 pieces) can be negotiated for testing.

 

Q: How to ensure the thread matching accuracy of non-standard square nuts and flange bolts?

A: We use pass-and-stop gauges to fully inspect threads, and provide a 6H/6g fit tolerance. For special-shaped fastener combinations (such as left-hand thread + square anti-loosening structure), assembly torque test reports can be provided.

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