Seattle Ultrasonics · Assisted Sharpening

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    Seattle Ultrasonics · Assisted Sharpening

    Before you start

    End User License Agreement

    Seattle Ultrasonics Assisted Sharpening

    Disconnect from the knife?

    Connect your knifeDone

    Pair with the C-200 over Bluetooth. While connected, the ultrasonics stay off — pressing the handle button won't run the blade.

    Remove & re-insert the battery

    First, put the knife in pairing mode: remove the battery, then re-insert it. Click Connect within 30 seconds of the battery going back in.

    Animation of the browser's Bluetooth window: C-200 appears in the list, is selected, then the Pair button is clicked.
    Then pick C-200 from the list and press Pair
    Update your knifeDone

    Checking for firmware updates…

    Firmware

    —

    Required

    Preparing…

    Keep this page open and the knife nearby until the update finishes.

    Zero on the stoneDone

    ⚠ Never lay the blade fully flat against the sharpening stone. This will scratch the blade.

    Lay the knife on its side so the handle sits flat on the stone. Then press and hold the handle button for about a second, and release to set the zero position.

    Knife laid on its side with the handle resting flat on the sharpening stone
    Handle flat on the stone
    Live roll—°Waiting for button press
    Choose your edge angleDone

    The C-200 ships with a 13° factory edge. A smaller angle is sharper but less durable; a larger angle is more durable but less sharp.

    13.0° / side
    Factory angle
    ← Sharper, less durableMore durable, less sharp →
    SHARPENING STONE
    Edge cross-section · closeup26° total included angle
    Sharpen

    Sharpen using even pressure across the blade, making use of as much of the stone surface as possible.

    🔊 Turn your volume upThe angle guide is mostly sound — it tells you where the edge is without looking at the screen.
    Target ±13.0° Side A
    0.0°
    Lift the blade toward 13°
    Δ —
    Stroke motion
    Side A0 cm Side B0 cm
    ✓Session results

    —

    —

    13°target / side

    Stroke motion by angle

    — on-angle

    stroke motion on angle

    Sharpening time—active sharpening
    Total stroke—both sides
    Side A——
    Side B——

    Seattle Ultrasonics · C-200

    © 2026 Seattle Ultrasonics · License agreement ·

    Reading your results

    The big number

    “46% on-angle” is the share of your stroke motion that landed inside the target band. It is measured by distance travelled, not by time — so resting the blade at a perfect angle without moving it cannot inflate the number, and only motion detected on the stone counts at all.

    It is a description, not a grade. A lower number on a tight band can be better sharpening than a high number on a loose one — which is why the band it was measured against is printed right underneath it.

    The curve

    Every stroke is filed by how far off your target angle it was, and the height of the curve is how much blade travel landed there. A tall narrow peak means a consistent angle; a wide or lumpy curve means the angle wandered.

    The green band is your tolerance zone and the orange dashed line is your exact target — the same target shown in the corner of the card. Anything left of the band was shallow (spine too low, a wider edge); anything right was steep (spine too high, a narrower, more fragile edge). The two percentages sit under the words at each end.

    The small V icon above the curve splits it into your two bevel sides, drawn on one scale. Two peaks in the same place means both sides were sharpened alike; peaks in different places means one side ran steeper than the other, which is what leaves an off-centre edge.

    The tiles

    Sharpening time is time the blade was actually detected on the stone — the number that reflects work done. The session total underneath includes setup, pauses and time in the air.

    Total stroke is the distance the blade travelled on the stone, and Side A / Side B split that per bevel. Sides that are far apart mean one got more work than the other; evening them out is usually what centres an edge.

    Ultrasonic odometer is lifetime run time on this knife, read from the knife itself — not a measure of this session.

    What to change next time

    Mostly shallow? Raise the spine slightly. Mostly steep? Lower it. A wide curve rather than an offset one is a steadiness problem, not an aim problem — slow the stroke down and let the sound guide you. And if the score looks unrealistically low, check that the tolerance in Settings matches the edge you actually want.

    Settings

    Guide

    Preferences are saved on this device and persist between sessions.

    Pro modeTighter target (±1.0°), 0.1° increments, and the stroke-distance readouts.
    Angle precisionIncrement for the angle picker and the live readout.
    Tolerance zoneHow far off angle still counts as “on angle” — the green band.
    Sound mode—
    Sound only on stoneStay quiet while the blade is off the stone.
    Show movement tracerThe small stroke-path canvas on the sharpening screen.
    Keep screen awakeHold the display on while you're connected to the knife.

    Help

    Intro videoThe quick tour that played on your first visit.

    Privacy

    Your browser is sending a Global Privacy Control signal, so we’ve turned this off. You can turn it back on if you want to.

    Send session dataSends your completed sessions — motion data, angles, and device details — to Seattle Ultrasonics so we can improve the sharpening guidance. Your on-screen guidance is calculated on your own device and works the same either way. Read the EULA

    Diagnostics

    Export the session that just finished, or load a recorded session (JSON) to replay its IMU stream through the full experience.

    cloud: —

    No file loaded.

    accel: —

    gyro: —

    roll: —

    stream: —

    knife: —

    contact: —

    Ground truth: hold the HANDLE BUTTON (or SPACE) while the blade is truly on the stone.

    Console