Stumbling upon the Hario Mini Mill tape mod didn’t happen through good science or strategic planning. It was mostly the result of not having a rubber band nearby. There is another mod out there that uses a rubber band to stabilize the inner burr, but I didn’t have one – so I just used tape. Then I figured I would try adding some tape to the metal rod. Thus, the tape mod was born.
The guide has been very well received. It’s been shared over 200 times in the last year (mostly on /r/coffee – thanks guys!) and has become the most visited article on coffeebrewguides.com! Despite all that, there hasn’t been any side-by-side testing done by anyone other than me. I did some testing when I first thought up the mod, but never published any proof of the results, until now.
I apologize for the pictures. I’m not a photographer. I’m a barista.
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.
At 10 clicks, the effect of the modification was showing. Before the mod, fines and boulders were both abundant. With the mod, both the fines and boulders are much closer to the intended size and less frequent, improving the grind uniformity.
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.
(click for larger image)
(mod on bottom)
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.