Installation Method for Captive Screws

I. Pre-Installation Preparation

表格

Item	Operation Key Points
Component Inspection	Confirm the screw, spring, and clinch bushing are intact without deformation; ensure the knurling of the thumb nut is intact, the spring elasticity is normal, and there is no rust or jamming.
Sheet & Hole Diameter	Match the sheet thickness (standard 0.5–3.0 mm); use the corresponding hole diameter (e.g., 3.1–3.2 mm for M3), tolerance ±0.05 mm; hole edge distance ≥ 1.5 times the outer diameter of the fastener.
Tool Selection	Clinching machine (manual/pneumatic/hydraulic) with special dies; torque wrench (torque specified per size); cleaning tools (deburring, degreasing).

Hole Preparation: Machining mounting holes by laser or punching, deburr and clean the hole wall and sheet surface.
Positioning & Clamping: Fix the sheet on the clinching machine table, align the hole with the die center.
Clinching Operation: Insert the captive screw, start the clinching machine and press evenly until the clinch bushing is fully fitted to the sheet with no gap; keep upper and lower dies parallel and complete in one stroke.
Self-Inspection: The screw is free of looseness and tilting; exposed height meets design requirements (tolerance ≤ ±0.1 mm); manual rotation is smooth without jamming.

Hole Preparation: Machine mounting holes with 45° chamfer; strict hole diameter matching is not required, and smaller edge distance is allowed.
Pre-Assembly Positioning: Insert the screw into the sheet hole, with the expansion ring on the outer side of the sheet.
Expansion Fixing: Apply even pressure with a special press punch to flare and expand the ring, firmly locking the sheet; suitable for flanged edges, thick plates (max. 5 mm), or painted sheets.
Self-Inspection: The sheet and expansion ring fit tightly without warping; the base of the screw does not wobble.

Pre-Positioning: Insert the captive screw into the mounting hole, press down firmly to compress the spring, turn clockwise for 2–3 threads, confirm thread alignment without jamming.
Final Tightening: Release pressure, continue tightening clockwise with a torque wrench; do not overtighten to the end, stop at the designed torque or when the mating surface is tight.
Function Test: Repeat loosening and tightening to confirm the screw does not detach, spring returns normally, and the connection is secure.

Torque Control: Strictly use specified torque (e.g., M6 approx. 8–10 N·m, M8 approx. 20–25 N·m); no violent tightening to prevent thread stripping or sheet deformation.
Anti-Loosening & Protection: For vibrating applications, use flat washers / spring washers; apply a small amount of anti-rust oil on threads (avoid cold welding for stainless steel); do not contaminate nylon locking components with oil or grease.
Troubleshooting:
- Loose clinching: Check die alignment, pressure parameters, or excessive sheet hardness.
- Thread jamming: Clean threads, inspect spring deformation, replace components if necessary.
- Risk of detachment: Confirm correct spring orientation and full clinching / expansion.

Secure Base: No obvious looseness or displacement when shaking the screw by hand.
Normal Function: The screw does not detach from the panel when loosened; no gap on the mating surface when tightened.
Appearance Compliance: No cracks or warping at the clinched / expanded area; the screw is perpendicular to the panel surface.