The blue inner ring on Fellow Opus 1 is not a second independent grind-size dial. It shifts the range of the outer ring, which lets you make smaller adjustments, extend the available range and compensate for long-term calibration changes.
How much does one inner-ring notch change?
Fellow says one Opus 1 inner-ring notch shifts the outer range by two-thirds of one minor outer increment. The outer dial has quarter-step increments, so one inner notch equals 1/6 of one numbered setting.
Fellow also describes the movement mechanically: one outer minor increment corresponds to about 50 microns of burr-height movement, while the inner-ring system splits that into roughly 16.7-micron steps.
How do you use the inner ring for espresso dialing?
Use the outer ring for the main adjustment. If one outer click is slightly too fine and the next is slightly too coarse, use the inner ring to shift the whole outer range between those positions.
Can the inner ring extend the total grind range?
Yes. Fellow says moving the inner ring to its extremes can allow Opus 1 to reach the equivalent of outer setting 0 or 12, beyond the printed 1–11 range.
How do you physically adjust it?
Fellow’s current procedure starts with an empty load bin and the outer ring centered at 6. Remove the load bin, press the two tabs of the blue calibration ring evenly until the spring-loaded mechanism bottoms out, then rotate the outer ring to shift the inner pointer. Release it so the ring re-engages, verify the mechanism moves together, and reinstall the bin fully.
When should the inner ring be used for calibration?
Fellow says prolonged burr wear can gradually make output coarser, and Opus 1 can be shifted finer with the inner ring. That is different from using the ring for a one-shot micro-adjustment.
Opus 1 vs Opus 2
| Feature | Opus 1 | Opus 2 |
|---|---|---|
| Blue inner adjustment ring | Yes | Do not assume same system |
| This article’s procedure | Applies | Does not apply |
| Calibration instructions | Inner-ring based | Use Opus 2-specific instructions |