We hope you have read through the Basic Instruction Manual for the Fixie Manual Coffee Grinder and have familiarized yourself with the Grinder, and the Adjustment Mechanism.  

Before getting into the nuts & bolts, we'd like to have a short discussion of our approach to the Fixie Disks, Tuner Shims, Grind Size, etc.  

Our goal with the Fixie Hand Grinder is that, in a sense, it 'normalizes' coffee brewing for many people.  A Fine, Medium, and Coarse (F, M & C) setting is quite approachable for many coffee drinkers.  The addition of the Tuner Shim system allows further adjustments to be made to do just that - Tune the grind to your preference, for your coffee, and for your device.   We have intentionally skewed the FMC settings in response to current trends in Coffee Brewing, which have gradually become 'grind finer' for almost all extraction methods.   Even Alan Adler, inventor of the Aeropress, is now advocating a much finer grind for his preference than he used to (like forever!)  Other examples of these types of finer grind approaches have been seen in many recent World Brewing Champion recipes for V60 or flat bottom brewers, using a finer grind, and in many cases a single pour rather than a pulse pour.  As the Fixie is designed as a Travel Grinder, it can be paired with a modern iteration of a Travel French Press - these newer presses have advanced filter systems that accommodate finer grinds as well.   Many feel that finer grinds lead to higher extraction yields (EY) and better taste.  Of course, there are many factors in play for making a good cup of coffee, and if it tastes good to you, that's all the matters!

When approaching the Fixie one must keep in mind that there is a direct relationship between the thickness of the Fixie Disk or Disk/Tuner set and the gap between the burrs.   BUT, burr gap is not the same thing as particle size - they are related, but not the same thing.  

A thicker disk creates a smaller gap by keeping the cone burr higher in relation to the ring burr.  
A thinner disk allows the cone burr to drop farther and creates a bigger gap between the cone burr and the ring burr.

So, lets look at some numbers.

The thickness of the Fixie Disks (+/- 0.02mm tolerance):
FINE - 4.2mm thick
MEDIUM - 3.5mm thick
COARSE - 3.00mm thick
The Tuner Disks have thickness of 0.10mm and 0.20mm (+/-0.01mm tolerance)  2 of each Tuner is included.

The addition of one or more Tuner Disks to a Fixie Disk will increase the total thickness of the Adjustment Stack, making the grind FINER (it makes the burr gap smaller when Tuners are added)

An operating example:
Coarse Fixie Disk, plus 2 Thick Tuner Shims, makes the stack 3.4mm.  (3.00 + 0.20 + 0.20 = 3.4mm)  When compared to the Medium Fixie Disk, it is one step ABOVE the Medium.  Medium is 3.5mm, our example stack is 3.4mm.

When working with the Medium Disk, if you add 2 thick Tuner Shims, the adjustment stack is 3.9mm (3.5 + 0.20 + 0.20 = 3.9mm)  

If you add all four Tuner Shims to the Medium Fixie Disk you will be one step above the Fine Disk (3.5 + 0.20 + 0.20 + 0.10 + 0.10 = 4.10mm)  The Fine Disk is 4.2mm, our example stack is 4.10mm.  

If you're following through all this, you may be able to see why we didn't put this in the basic manual - it's easy to glaze over dealing with too many numbers!

You may have noted the Fine Disk at 4.2mm is out of sequence.  Standard sequence would be F=4.0 instead of 4.2  We did this so that the Fine Disk would be adequately Fine for Aeropress for most people in normal usage, and also to allow one to hit Turkish, or Near Turkish using the Fine Disk and 4 Tuner Shims.  

Greater adjustability can be achieved using thinner shims.   The Tuner Shims are made of Teflon, and they are of specific thickness.  When you reduce the thickness below 0.10mm almost all shimming material is fairly fragile - once installed in the grinder, thinner material is not a problem because it is sandwiched between the Fixie Disk and the Drive Disk, but we wanted to provide Tuners that could stand up to normal use by the average consumer.   

Where the adjustability becomes an issue is, or course, if you want to use the Fixie to grind for Espresso.  We acknowledge that there are many people who travel with an Espresso Kit.  If you Travel with Espresso, you have gone the extra mile to have your favorite beverage on the road, the hike, or the seas, and we assume you are willing to go that extra mile to dial in the Fixie for your Espresso needs!

A quick Google, or some time with a Caliper will provide you with plenty of sources for Tuner Shim Material - Old School Machinists like to say that a cigarette rolling paper is .001" (.024mm)  Sounds a bit fragile, but once cut & installed in the stack, it will work fine.  Standard household Aluminum Foil is about 0.016mm thick, Heavy Duty household Aluminum Foil is about 0.024mm thick.   There are also many places to purchase professional shimming materials that have very high specificity of thickness.   

Since we are in an area that we have labeled 'advanced', we would also add that if you have dialed in for espresso, and you go on remote with that one setting you likely will also control your espresso shot using  up dosing, down dosing, pre-infusion period control, etc... 

Additionally, if you require Coarser grinds than what we have provided with the Coarse Fixie Disk you can substitute a thinner Coarse disk for the one we provide...  But from our experience a Coarse Disk of 2.0mm when combined with a conical burr system may provide a somewhat inconsistent grind.  A Coarse Disk of 1.0mm and you'll end up with a bunch of boulders and half cracked beans...so we don't provide them!  

We hope we haven't made this sound overly complicated, because once you understand how to use the Disk/Tuner system it's really quite easy!
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