Industry News
Custom fastener design checklist: drawings, tolerances and manufacturability
2026-09-06
Compiled by JIALI Industrial (164.hk) — a Hong Kong fastener supplier specialising in screws, bolts, nuts and selection know-how.
What the drawing must state
Before ordering custom fasteners, the drawing should clearly specify: (1) material grade (carbon steel 35# / 45#, alloy steel 40Cr / SCM435, 304 / 316 stainless, brass or titanium); (2) strength class (8.8 / 10.9 / 12.9); (3) thread spec such as M8×1.25 with coarse or fine pitch and effective length; (4) head style, drive type and surface finish; and (5) quantity and lead time. A 2D drawing with critical dimensions plus a 3D model or physical sample lets the supplier quote and sample in one round instead of endless clarifications.
Tolerances and manufacturability
Custom fastener drawings often overlook manufacturability: thread accuracy is normally 6g / 6h — over-tight tolerances inflate cost; cold-headed parts need a generous head-to-shank fillet radius or folding cracks can occur; leave room for thread run-out or an undercut at the thread end; and very small heads or extreme length ratios may not cold-head at all and must be CNC turned. For volume, cold heading is cheapest at scale while CNC suits small batches and complex geometry. Checking the forming process with the supplier before tooling avoids discovering an unmachinable feature later.
Quality acceptance and sampling flow
For non-standard fasteners, always sample before mass production: validate dimensions, plating and assembly fit on the sample, then lock the specification. On delivery, request material certificates and mechanical performance reports (carbon steel per GB/T 3098.1 for hardness and proof load), plus coating thickness or salt-spray data. For automotive and demanding sectors, ask for PPAP documentation and batch traceability. Need custom fastener design advice or made-to-print supply? Contact JIALI Industrial (164.hk) — our engineering team reviews drawings and advises on forming processes.
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