Knurled Cylindrical Or External Hexagonal Locking Screws And Nuts

Product introduction

This product is a screw with a special shape. The screw and nut are precisely locked together. After installation, the surface on both sides is smooth and beautiful, with no bulges. Suitable for furniture, guardrails, electronic chassis and other occasions that require high appearance. As a typical non-standard screw, it breaks through the traditional "bolt + independent nut" separate design, and can customize non-standard length, thread specifications, head shape (countersunk head/semi-round head/inner torx) and nut shape (knurled cylindrical/external hexagonal). We support the development of customized non-standard screws. We provide 304/316 stainless steel or carbon steel materials according to your connection material, thickness and installation space. We can control quality according to ISO 9001 and IATF 16949 systems.

 

Product design and features

Product structure composition:

The locking screw nut is a special fastener combination consisting of a screw (male part) and a nut (female part) -1-6. Its core structure includes:

Screw part (male part): The head is usually flat head, countersunk head, semicircle head or internal hexagonal shape, and the stem has precision external threads -1

Nut part (female part): The outer part is cylindrical or hexagonal, and the inner part has internal threaded holes matching the screws -2

Locking principle: During installation, the screws and nuts are locked relative to each other from both sides of the connected object, and the internal threads inside the nut fully engage with the external threads of the screw to achieve a smooth connection on both sides.

Product Features - Why it is a "specially shaped screw"

Traditional screws and nuts need to be accessed on both sides, and the nuts are usually located on the outside of the connection. The locking screws and nuts adopt an internal and external thread locking structure, and the surfaces on both sides can remain smooth and beautiful after installation. This makes it impossible to find the exact corresponding model directly in the standard manual of ordinary fasteners, so it belongs to the typical special shape screw-10.

 

Its special features include:

Integrated locking design: Screws and nuts are precisely matched through internal threads, which is different from the traditional "bolt + independent nut" combination.

 

Materials and application areas

Commonly used materials:

SUS304 stainless steel: good corrosion resistance, medium strength, non-magnetic furniture, guardrails, outdoor facilities, food machinery-1-6

SUS316 stainless steel: resistant to salt spray, acid and alkali (especially chloride ion environment) ships, coastal facilities, chemical equipment-4-8

Carbon steel (10B21/35K): high strength, heat treatable, low cost, general industrial equipment, auto parts

SCM435 alloy steel: high strength, high wear resistance, HRC35-42 heavy machinery, automobile and motorcycle parts, engineering vehicles-4

Brass/Bronze: no sparks, corrosion resistance, good electrical conductivity, electronic equipment, explosion-proof places

Aluminum alloy: lightweight, suitable for weight-sensitive equipment, aerospace, high-end competition equipment

 

Application areas

Furniture manufacturing: connectors for plywood beds, office chairs, cupboards, and showcases—requiring smooth and beautiful surfaces after installation-1

Guardrails and curtain walls: docking and fastening of glass guardrails, laminated glass curtain walls, and stainless steel railings-1-9

Electronic appliances: chassis casing, power module, control cabinet panel - required to be beautiful and not scratch the wiring harness

Automobiles and auto parts: interior panels, seat frames, connections between plastic parts and metal parts

Architectural decoration: cross-fixing of stair handrails, sunrooms, and display racks

 

Quality control and certification system:

Test items and methods

Dimensional accuracy: Use a three-dimensional coordinate measuring instrument to detect the thread pitch diameter, head profile, nut outer diameter and concentricity

Fitting performance: The pass-stop gauge fully checks the threads to ensure that the male and female parts fit smoothly and without shaking.

Mechanical properties: Guaranteed load test, torque test (to verify the torsional strength of the head and rod)

Hardness testing: Vickers or Rockwell hardness test to ensure that the heat treatment process meets the standards

Corrosion resistance: salt spray test (304 material ≥ 240h, 316 material ≥ 720h without red rust)

 

Certification qualification:

ISO 9001:2015 (whole-process quality management system)

IATF 16949 (Special requirements for the automotive industry, applicable to vehicle-mounted locking fasteners)

RoHS/REACH (environmental compliance)

 

Customized services:

Size: Any thread specification (M2~M16), any total length, non-standard head diameter/nut outer diameter

Thread type: metric coarse/fine thread, inch UNC/UNF, self-tapping thread, left-hand thread

Head type (screw): flat head, countersunk head, semi-round head, large flat head, inner hexagonal, inner torx, straight/cross, T-shaped head-1-6

Nut shape: cylindrical knurl, external hexagonal, hexagonal flange, circular grooved, gear-shaped-2-7

Material and treatment: stainless steel/carbon steel/alloy steel/brass/aluminum alloy, surface treatment: passivation/galvanized/nickel plated/Dacromet/blackened

Additional functions: pre-coated with anti-loosening glue, head engraving/logo engraving, nut with anti-slip teeth, magnetic adsorption

Special-shaped design: can be designed with complex structures such as positioning bosses, eccentric holes, special-shaped grooves, etc.

 

Customization process:

Requirement input: Provide drawings, samples or detailed description of working conditions (connector material, thickness, installation space, environmental requirements, etc.)

DFM analysis: evaluate the production process route (cold heading, precision turning or combined process) and give manufacturability recommendations

Sample manufacturing: 10-50 samples delivered in 10-20 days

Installation verification: Customer tests the matching performance and installation process

Mass production: MOQ is generally 3000-5000 pieces, complex non-standard screws can be negotiated for trial production of 1000 pieces

Customized case: An outdoor furniture customer needs a M6×35mm locking screw nut, which is made of 316 stainless steel, has a torx countersunk head, a cylindrical knurled nut with anti-slip texture, and an overall salt spray resistance of 720 hours. This is a typical customized non-standard screw. We completed it from design to delivery in only 18 days.

 

FAQ

Q: Why are locking screws and nuts called "specially shaped screws"? Are there no ordinary standard parts?

A: Standard screws and nuts are separate, independent products. The locking screws and nuts adopt an integrated locking design. The screws and nuts are matched through precision internal threads. They are combined fasteners. The corresponding model cannot be directly found in the standard parts manual. So it is a specially shaped screw-10. If you also need non-standard sizes or special head shapes, it becomes a non-standard screw; if it is completely customized according to your working condition parameters, it is a customized non-standard screw.

 

Q: What is the difference between locking screws and nuts and ordinary bolts + nuts?

A: There are three main differences: ① Appearance - both sides of the locking screws are flat and beautiful after installation, while ordinary bolts and nuts are convex on one side; ② Fitting accuracy - the locking screws are specially matched and the fit is tighter; ③ Anti-loosening - the locking structure itself has certain anti-loosening properties. Ordinary bolts and nuts require additional washers or glue.

 

Q: Can it be used outdoors? How is the corrosion resistance?

A: Yes. We provide SUS304 and SUS316 stainless steel materials -4-8. The 304 material is suitable for general outdoor environments (salt spray for 240 hours), and the 316 material is suitable for strong corrosive environments such as coastal and shipbuilding (salt spray for 720 hours without red rust). For extreme corrosive conditions, special surface treatments such as Dacromet coating can also be customized.

 

Q: Can the locking screws and nuts be disassembled and reused?

A: Yes. The design of the locking screw and nut supports multiple disassembly and reinstallation without affecting the locking performance. However, if the anti-loosening requirements are extremely high (such as vibration equipment), it is recommended to replace the model with pre-coated anti-loosening glue after disassembly.

 

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

A: - Regular stock specifications (such as M4×20mm, M6×30mm): starting from 100 sets

Non-standard screws (only non-standard sizes): starting from 3000 sets

Specially shaped screws (special head shape or nut shape): starting from 5,000 sets

Customized non-standard screws (completely customized according to drawings): starting from 8,000 sets, sample order can be negotiated (100-200 sets)

 

Q: How to ensure the matching accuracy of screws and nuts?

A: We use thread passage and stop gauges to randomly inspect each batch of products (full inspection is available for special orders), and use a projector or three-dimensional coordinate measuring instrument to detect the concentricity of the inner and outer diameters. For customized non-standard screws, we will provide a first article inspection report containing measured data of all critical dimensions.

 

Q: Can the locking screws be customized in different colors?

A: Yes. We provide surface treatment services: zinc plating (blue/white/yellow/black), nickel plating (bright nickel/nickelless), Dacromet (silver gray/black), and black oxidation blackening treatment. Can be customized according to customer color card. This also falls into the category of customized non-standard screw services.

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