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

Troubleshooting

Cracks Appearing After Forging

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.

Forging and bladesmithing in a working knife shop
If a symptom appears mid-job, put the work down and check it before continuing.
Cold forged steel bar on a dark bench with a ground corner window showing a fine hairline crack

The flow

Work it in this order

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

  1. Likely causes

    Forging below dull red (the number-one cause — cold steel tears instead of flowing). Burnt spots from welding-heat corners (steel that sparkled in the fire is dead). Accumulated forging stress never relieved by normalizing. Drastic cooling (hot bar on cold concrete or an impatient dunk). Or the steel itself — mystery scrap with fatigue history.

  2. Quick checks

    Grind a clean window and etch it — cracks show as sharp dark lines. Wipe with penetrating oil, wipe dry, and watch the crack weep it back out. A file dragged across a suspect line catches on a real crack. When in doubt, snap-test a coupon from the same bar and read the grain.

Gloved hand holds a grimy wipe beside a blade blank whose wiped window shows a hairline crack with amber oil along it.

  1. Fixes

    End and corner checks: cut back to sound steel and continue — this is routine, not failure. Cracks in the intended blade body: scrap it honestly. There is no fix that makes cracked steel trustworthy; steel is cheap and your name is not.

Short cracked steel offcut lying apart from a sound square bar, with a hand hacksaw behind on a dark bench

  1. Prevention

    Stop hammering at dull red, always. Watch corners and thin sections at high heat — they overheat first. Normalize with descending thermal cycles after forging, cool in still air, and start from known steel. Most crack problems are the same three habits wearing different disguises.

Rough-forged flat steel bar resting on two ceramic crossbars of an open iron rack, standing in a tray on a dark bench.

  1. When to stop

    Any crack that survives grinding into the final blade envelope ends the blade — and remember the quench multiplies whatever cracks you carry into it. Cut back or start over before heat treat, never after.

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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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  • Classic aluminum 2x72 grinder, side view with flat-platen tool arm and yellow Safety Rules label, on black with a purple glow

    Torus 2×72 Classic Aluminum Belt Grinder

    Prior-design aluminum chassis, 90-degree tilt and 1.5-inch tooling arms.

    Starts at$995View

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Send me a photo and describe what happened before it went wrong. Include the machine, belt and steel when they are relevant.

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