At HETAI, a clear and complete technical drawing is one of the most important documents for manufacturing custom fasteners. A detailed drawing allows our engineers to understand the exact requirements of the product, select the appropriate manufacturing process, and establish the correct inspection standards.

A custom fastener drawing does not need to be unnecessarily complicated, but it should clearly define all dimensions and technical requirements that can affect manufacturing, assembly, performance, and quality.

1. Overall dimensions and geometry

The drawing should include all critical dimensions of the custom fastener, such as overall length, head diameter, head height, shaft diameter, hole diameter, step dimensions, chamfers, radii, and other special features.

For products with complex geometries, sectional views or enlarged details can help clearly show features that are difficult to understand from the main view.

2. Thread specifications

Thread information is essential for bolts, screws, nuts, studs, and other threaded components. The drawing should specify the thread type, nominal diameter, pitch, thread length, tolerance class, and whether the thread is internal or external.

For example, the drawing may specify metric coarse or fine threads, UNC, UNF, or a special non-standard thread. If a product requires different thread specifications on each end, this should also be clearly indicated.

3. Material and mechanical requirements

The drawing should identify the required material grade and, where applicable, mechanical requirements such as tensile strength, yield strength, hardness, or fastener property class.

For example, a customer may specify carbon steel, stainless steel, alloy steel, brass, or another material, together with requirements such as property class 8.8, 10.9, or 12.9.

If heat treatment is required, the relevant hardness or heat-treatment condition should also be stated.

4. Dimensional tolerances

Not every dimension needs the same tolerance. Critical dimensions should have clearly defined tolerances so the manufacturer knows which features require tighter control.

At HETAI, achievable tolerances depend on the manufacturing process, material, product geometry, dimensions, and application. Suitable standard cold-forged fasteners may achieve approximately ±0.01 mm, while CNC-machined custom fasteners may achieve approximately ±0.005 mm. Precision hardware components processed through grinding may reach approximately ±0.002 mm for suitable features and applications.

If a specific tolerance is important for assembly or function, it should be clearly marked on the drawing.

5. Surface treatment and finish

The drawing should specify the required surface treatment or finish, such as zinc plating, nickel plating, black oxide, passivation, anodizing, or other specified finishes.

Where necessary, the drawing should also indicate coating thickness, color, corrosion-resistance requirements, or other relevant surface-treatment specifications.

6. Applicable standards and technical requirements

If the custom fastener must comply with a particular standard, the drawing should clearly identify it. This may include ISO, DIN, ANSI, ASTM, JIS, or customer-specific specifications.

Additional requirements such as thread standards, inspection methods, packaging requirements, or special quality criteria can also be included in the technical notes.

7. Quantity and application information

Although quantity does not always need to appear on the drawing itself, providing the required production quantity and intended application helps HETAI select an appropriate manufacturing process.

For example, low-volume prototypes may be more suitable for CNC machining, while high-volume production may benefit from cold heading or other dedicated forming processes.

What should you send to HETAI?

For a quotation and technical evaluation, we recommend providing a 2D engineering drawing or 3D CAD file, together with the material, quantity, surface treatment, applicable standards, and any special technical requirements.

If a formal drawing is not available, HETAI can also evaluate a physical sample, sketch, or reference component and discuss the required specifications with the customer.

The more clearly the technical requirements are defined, the easier it is for HETAI to select the right manufacturing process, accurately calculate the quotation, and ensure that the finished custom fastener meets the required dimensional and functional requirements.