Heavy Metal: The Tech Diver’s Guide to Rigging

Top Tips: Checking Your Springs (The Bolt Snap Health Check)

A bolt snap is a simple mechanical device holding life-support equipment worth hundreds of pounds. When a spring fails, it usually happens in one of two ways:

1. The “Open Fail”: The gate sticks open, and your stage cylinder falls to the seabed (or onto a wreck 40m below).
2. The “Seized Fail”: The gate refuses to open, trapping you attached to a shot line or reel.

In the UK, where silt and salt work together to destroy moving parts, you cannot wait for a failure. You must predict it. Here is the 60-second health check for your hardware.

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1. The “Crunch” Test (Audible Diagnosis)

You can hear a failing clip before you can see it.

• The Action: Hold the clip close to your ear. Pull the trigger back and release it slowly.
• The Pass: Silent, smooth motion.
• The Fail: A “gritty” sound or a sensation of grinding. This means salt crystals or silica (sand) have worked their way into the internal piston chamber.
• The Fix: Soak in hot water and vinegar. If the crunch persists after lubrication, the internal barrel is scored. Bin it.

2. The “Lazy Gate” (Spring Fatigue)

Springs lose their “memory” over time, especially if stored under tension (e.g., clipped onto a thick D-ring for months).

• The Action: Pull the gate back fully and release it gently (don’t let it snap).
• The Pass: The gate returns fully to the closed position, touching the hook.
• The Fail: The gate stops 1mm–2mm short of the hook, leaving a tiny gap.
• The Danger: That tiny gap is a line trap. Fishing line or caveline can slip in, but it won’t slip out. If a gate doesn’t slam shut with authority, the spring is dead.

3. The “Side-Wiggle” (Rivet Wear)

The gate is held by a pin/rivet. Over thousands of cycles, the hole elongates (becomes oval).

• The Action: With the gate closed, try to wobble the trigger mechanism side-to-side.
• The Pass: Minimal movement (tight tolerances).
• The Fail: Significant lateral play.
• The Danger: If the gate wobbles, it can twist sideways under load, jamming the piston against the barrel walls. You will be unable to open the clip when you need to ditch a cylinder.

4. The “Rust Weep” (Internal Corrosion)

Even in 316 Stainless Steel clips, the internal spring is often made of a different steel alloy (high carbon) to maintain its “bounciness.” This spring can rust.

• The Action: Inspect the seam where the sliding piston enters the barrel.
• The Fail: If you see a brown/orange stain “weeping” out from the internal mechanism, the spring is disintegrating. It will snap soon.
• The Rule: External rust on the surface is cosmetic. Internal rust “bleeding” out is terminal.

5. The Magnet Test (Material Verification)

Not all “Marine Grade” clips sold online are genuine AISI 316.

• The Action: Touch a strong magnet to the body of the bolt snap.
• The Result:
  • 316 Grade: The magnet should not stick (or have an extremely weak pull).
  • 304/Cheap Steel: The magnet will stick firmly.
• Note: The internal spring will be magnetic. Ensure you are testing the solid body loop. If the body is magnetic, it will rust within a month of UK diving.

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Summary: When to Retire a Clip?

Symptom	Diagnosis	Solution
Gritty Sound	Internal debris	Soak in vinegar. If noise stays, replace.
Gap at closure	Spring fatigue	Immediate disposal.
Orange Weeping	Rusted spring	Immediate disposal.
Stiff Action	Lack of lube	Apply food-grade silicone grease.
Wobbly Gate	Worn rivet	Relegate to “dry land” use (keys) only.