Short answer: Slowly. Binary search. But for espresso, Turkish, moka, or AeroPress: I adjust mine to nearly the tightest (smallest) setting possible that still allows me to turn the crank without difficulty.
Method: This is how I adjust mine.
- Approximate the setting by eye. Looking at the burrs, gauge about how large you'd like your grounds to be.
- Mark this setting (temporarily) with a wax pen or marker.
- Grind a bit of coffee and look at the average grind size; determine whether you'd like it coarser or finer.
- Change the setting by N (e.g., 4) steps in one direction.
- Repeat. Grind a bit more coffee. If you went in the correct direction (finer or coarser), determine whether you'd like it finer or coarser. (Start over if you went in the wrong direction)
- Change the setting by going N ÷ 2 (e.g., 2) steps in that direction.
- Repeat the grind and check. Terminate if you're happy, or go one step at a time until you are happy.
- MARK THIS SETTING AND HOPE YOU NEVER HAVE TO CHANGE IT ;-)
My experience: I have a similar Hario model (this one), which sounds marginally more difficult to adjust than the one you're talking about. I use mine for almost all of my daily coffee grinding. I set it very infrequently: I go through phases between pour-over and moka, and I try not to go through these phases more than once per month to avoid adjusting this thing.
To adjust my model:
- Remove top nut.
- Remove crank handle.
- Remove setting bracket.
- Twist the toothed, threaded washer/nut about the threaded shaft to move the nut up (counter-clock, coarser grind) or down (clock-wise, finer grind).
- Replace bracket, handle, top nut.
I mark the "set-screw" nut with a marker to remember where I've tried. I try to avoid going more than one revolution either way; on mine, two revolutions goes from moka-fine powder to French-press coarseness.
When you've figured it out... I have put scratch "marks" on the screw for I (moka: fine), II (drip: medium), III (French press: coarse) so that I don't have to guess quite as much. Highly recommend indelible marks on your grinder once you find the setting you like. To change from one setting to the other, adjust to the middle: then go tighter to the "fine" setting, and looser to the "coarse" setting (otherwise, it can be ambiguous).
Other than changing the settings, I like the thing. There was even a Kickstarter that funded a stabilizing mechanism for the bottom to ensure a more-even grind: it launched as EvenGrind (I have no affiliation with it).