This is for all those Hario Mini Mill lovers who are curious how to make their hand grinder significantly more consistent by using simple mods to the rod and outer burr.
If you’re not an owner of this fantastic hand grinder, check out its review!
UPDATE: The new Hario Mini Slim resolves a lot of the issues that this mod guide used to resolve. While this mod will still work for older grinder models, I largely just recommend upgrading to the new, far-better version 🙂
Back to the Hario grinder mod guide!
The Problem: Achieving a Consistent Grind Size
It’s no secret that the Mini Mill doesn’t exactly compete with a commercial electric grinder, but this little guy is definitely good enough for most people.
There is one problem however: grind consistency.
Consistent coarse grind size tends to be fairly inconsistent with many different sized grounds.
This problem is a result of two pieces, the metal rod and the outer burr, not being set in their places firmly enough. This enables some wiggling, which ends in unevenly ground coffee.
The Solution: Scotch Tape
The solution is so simple you will doubt it: scotch tape. Yes, those clear strips are the key to the Hario Mini Mill mod.
Step 1: Disassemble Your Hario Mini Mill
Before we apply tape, disassemble your hand grinder and clean it well.
Don’t use water on any of the ceramic pieces, it could shorten the grinder’s life. I just use a paper towel and little brush to get small particles off.
The two pieces you’ll need for this modification are:
- the long metal rod
- the outer burr (the large ceramic ring)
Step 2: The Metal Rod Mod
This part is fairly simple. Right above the screw portion of the rod are two small protrusions on either side. Just above this is where the tape is going around the rod. Put just enough on so that the rod can fit through the black hopper and spring, but be set firmly. I used about four layers of tape, but experiment yourself to find the best fit.
Once you’ve done that, place it back through the tunnel and attach the pieces that hold it in place. You should be able to notice much less wiggling.
Step 3: The Outer Burr Mod
This part is a little more difficult.
Split a piece of tape into two long strips using scissors. Make sure not to cover the indentions where the burr and body meet. Take your time and try not to allow lots of tape going over the edges. Here I used three layers.
After you’ve applied this mod, settle it back into the bottom of the body and confirm that the wiggling has decreased immensely. If not, apply another layer of tape. As before, experiment!
Step 4: Reassemble your Hario grinder
After reassembling you’ll notice that the coffee grounds are much more consistent, especially when you’re grinding coarsely.
And that’s the Hario Mini Mill mod!
Modded Mini Mill vs Non-Modded Mini Mill Grind Comparison
Skeptical of this mod using extremely simple materials? I completed a side-by-side comparison of the grind uniformity of a modded Mini Mill vs a non-modded Mini Mill and recorded my results. Check out the Hario Mini Mill Mod Grind Comparison!
Note* My access to resources and technologies (micron filters and such) that could measure the effectiveness of the modification using standard scientific measurements is non-existent. As a result, these results are based on eyesight and feel.
Below is a brief summary.
Grind Setting: 5 Clicks
I found that the modification didn’t seem to change much at only 5 clicks.
With the burrs tightened to this degree, the modded components weren’t increased in efficiency, at least not that I could tell with the naked eye.
Grind Setting: 10 Clicks
At 10 clicks, the effect of the tape modification was showing.
Before the mod, fines and boulders in the ground beans were both abundant. After the mod, both the fines and boulders are much closer to the intended size and less frequent, improving the overall grind uniformity.
Grind Setting: 15 Clicks
At 15 clicks, the modification is essential.
Without it, fines and boulders are everywhere, and grind uniformity is nowhere to be found. With the modification, this setting is actually usable, although probably too coarse for most brewing methods.
Additional Tips for a More Consistent Grind
I’ve discovered a couple extra things that help with grind uniformity when using the Mini Mill.
1. Use a Solid Surface When Grinding
It seems that using both arms to swing the grinder around to achieve a very quick grind is not ideal for consistency. Placing the grinder on a solid surface like a counter or table while grinding seems to be makes a noticeable difference, although it requires more effort.
For speed, swing like a madman.
For consistency, let gravity pull the beans down naturally.
2. Maintenance and Cleaning
Take care of your grinder, and it will take care of you.
This includes unwrapping the scotch tape and reapplying more after a quick cleaning. Resist the temptation to use water on the ceramic parts and invest in a toothbrush you can use on your coffee equipment to knock off fine particles.
If there are any stuck crumbs, you can use the tip of a butter knife to gently scrape them off.
Bottom Line on Improving the Grind Quality with this Mod
This mod shines at coarser settings, and is useful at finer ones. My test results were somewhat impacted by my grinder’s burr sharpness and the beans that I used. I am certain that newer and older devices will both be improved by implementing the mod.
Has anyone else conducted a similar test, have questions, tips or tricks? As always, if you know of any other tricks or ways of improving the daily grind, post in the comments!
Good luck, and happy brewing!