A well-written specification saves time, reduces cost, and ensures delivered parts match the design intent. Yet many engineering teams submit drawings with incomplete or unrealistic requirements. This guide outlines essential parameters for specifying custom turned pins, shafts, and bushings for precision equipment.
1. Diameter and Tolerance
Specify the nominal diameter and the tolerance range. For precision alignment applications, we recommend ±0.01mm to ±0.02mm. For general positioning, ±0.05mm may be sufficient. Over-tolerancing features that do not require high precision adds unnecessary cost.
2. Length and Critical Dimensions
Indicate overall length and any critical step dimensions. For multi-diameter parts, specify which diameters are functional bearing surfaces and which are clearance or retaining features. This allows the manufacturer to prioritize inspection on critical features.
3. Material and Hardness
Specify the material grade. For stainless steel, use specific grades such as 303, 304, or 316. For carbon steel applications, specify 10B21, 11SMn30, or 100Cr6 if heat treatment is required. If hardness is important, state the target HRC range.
4. Surface Finish and Coating
Specify surface roughness requirements. Ra 0.4μm is typical for bearing surfaces; Ra 0.8μm is sufficient for general applications. For corrosion protection, specify zinc plating, zinc nickel plating, or passivation. Include salt spray test requirements if applicable.
5. Knurling and Other Features
If knurling is required, specify the pattern (straight or diamond) and the knurling pitch. For threaded ends, specify the thread standard and class. For retaining grooves, provide the groove width, depth, and position relative to the end face.
6. Quantity and Lead Time
Be realistic about volume. At Tingfeng Hardware, we accept orders from 200 pieces, but pricing and lead time are directly tied to batch size. Indicating annual usage helps us recommend the most cost-effective approach.
7. Provide a Clear Drawing
A dimensioned drawing (or 3D model) is the most effective way to communicate your requirements. Acceptable formats include PDF, DWG/DXF, STEP, and IGES. Include tolerances, material notes, and any special instructions.
Conclusion
A complete specification helps us provide accurate quotations and deliver parts that perform reliably in your precision equipment. We welcome engineers to contact us with their requirements, even at the early concept stage, for design for manufacturability feedback.