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Nebula dual-axis tracking assembly: star knob, spring and idler wheel, close-up, on black with a purple glow

Troubleshooting

Folder Lock Rock & Blade Play

Work back from what it is doing to what caused it, then to the fix that addresses the cause. Nothing here needs a sign-up.

Folding knife mechanisms in a working knife shop
If a symptom appears mid-job, put the work down and check it before continuing.

The flow

Work it in this order

Causes first, then the quick checks, the fix, prevention and the stop-work point.

  1. Likely causes

    Two different diseases sharing symptoms. SIDE-TO-SIDE play is the pivot stack: pivot tension backed off, washers worn or never flattened, tang flats burred, or a stretched cheap pivot. LOCK ROCK (the click-seat under pressure) is the lock interface: a lock face fitted at too little contact or too steep an angle on a liner or frame lock, a worn or sloppy notch on a lockback, or early engagement that never bedded flat. VERTICAL play is stop geometry - stop pin or kick fit. New-build lock rock is almost always an unresolved lock-face fit; aged-in play is almost always the pivot loosening.

  2. Quick checks

    Sort the disease first: close the knife and wiggle the blade at the tang - play while CLOSED is pure pivot stack (the lock is not even engaged). Open, then press the spine gently: a click-and-seat is lock rock. Watch the lockbar as you press - does it slide deeper across the tang? Check pivot screw tension before anything structural.

Gloved hands hold a closed folding knife flat on a dark bench mat, one thumb pressing at the pivot end of the handle.

  1. Fixes

    Pivot-stack play: tighten in eighth-turns to zero-play-free-drop, and if tension will not hold, disassemble - flatten and polish the washers, deburr the tang flats, replace a stretched pivot - per the tuning sequence. Lock rock on a liner/frame lock: re-fit the lock face by marker-blueing to flat bedded contact (a too-steep face gets re-ground shallower; engagement that starts past mid-tang means the face angle or bar length needs work); on a lockback, the notch-and-lug interface gets the same blueing treatment. Vertical play: address the stop pin fit or kick. The discipline: fix the pivot stack FIRST - lock symptoms diagnosed through a loose pivot are lies.

Disassembled folder parts on a dark bench: a blade with blue tape on the edge, a blued tang lock face and the liner beside it.

  1. Prevention

    Fit lock faces by blueing at build time to 25-50% flat engagement. Flatten washers before first assembly. Thread-locker at proven-final tension. Fifty-cycle checks before any folder ships, and a re-check habit at every sharpening.

Thumb presses a bronze pivot washer flat on a gray abrasive sheet bonded to a steel plate, with a second washer in a tray.

  1. When to stop

    A lock that disengages under firm hand pressure is failed, not tunable - refit or retire. And a frame/liner lockbar bent past its spring range (from forcing or a drop) is a replacement, not an adjustment; spring steel remembers abuse.

Detached steel folder liner on a dark padded mat, its lockbar lifted by a sharp permanent kink near the base.

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Guides that cover the cause

The long-form version of the fix above, written from the same bench.

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Same bench

When the machine is the cause

Flex, a soft platen or a tracking knob that will not hold can show up as a bad grind. I machine the parts, hand-assemble, track and test each Torus grinder in Sterling, Illinois.

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    Torus 2×72 Classic Aluminum Belt Grinder

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