Coffee Grinder Burr Hack

CAUTION: Sharp edges are created during this operation and sharp tools are used. Wear appropriate PPE (e.g. leather gloves).

CAUTION: Deenergize (unplug) your grinder before working on it.

CAUTION: Adding shims increases the probability of collisions within your burr set. Collisions will cause irreparable damage to your burrs and may also damage your motor. IF you believe your burrs are contacting one another, DO NOT start your grinder and remove the shim(s).

Problem/Observation:

I was frustrated that I couldn't quite get an espresso grind with my cheap conical burr grinder (Ariete Grinder Pro). All of my espresso shots were pulling in about 15-20 seconds when in general one is looking for a 30-second extraction; the extraction is happening too quickly leading to under extraction.

Hypothesis:

The cause of the problem is the lowest setting on my grinder was just out of reach of an espresso grind. This decreases head loss and decreases the time it takes to pass a fixed volume of hot water through the coffee bed.

Decreasing the size of the grains, i.e. a smaller grind, will increase the contact time and lead to more ideal extraction.

Solution/Experiment:

Aluminum can walls have a very consistent thickness and are generally in the range of 4 thousandths of an inch (in machining language); typically around 0.0038 inches (a touch smaller than 0.1 mm), which is a great material to use for making very thin shims. The material is dimensionally stable under compression, easy to cut, cheap, easy to find, and resists corrosion. The galvanic potential between the stainless material of the burr and the aluminum is unknown; however, the polymer coating on the interior side of the aluminum will resist contact between the dissimilar metals eliminating it as a failure mode.

I cut a shim out of an aluminum soda can and placed it between the upper burr set and the mounting.

Results:

Espresso shots now pull in approximately 30 seconds.

• Aluminum can, preferably from seltzer water (to avoid needing to clean sticky sugar.)
• Tin snips
• Exacto knife or box cutting blade.
• Necessary tools to disassemble your burr grinder, for me it was a Philips screwdriver.

1. Remove the burr. On my grinder, removal is an easy 1/8 turn after removing the coffee hopper.
2. Disassemble the burr from the mounting/setting. On my burr, it was two Philips head screws.

CAUTION: Sharp edges and sharp tools. Wear proper PPE

1. Using a set of tin snips, I cut open the aluminum can. (I believe a standard pair of scissors may cut an aluminum can. However, tin snips are purpose-made for cutting metal. You may damage a pair of standard scissors if you decide to use them.
2. Trace the profile of the face of the burr onto the aluminum can.
3. Cut the inner portion out. I used a disposable box cutting blade to score the aluminum and then a pair of plyers to pull out the center. The can will tear where you've scored the surface with a knife (the tear will follow the surface defect). Be sure to cut this a touch larger as you don't want any portion of shim to be sticking out when you reassemble.
4. Use tin snips to cut the outer part of the pattern.

1. Place the shim between the mounting/setting and the burr and reassemble. CAUTION: The aluminum shim is very sharp.
2. Assess and check the burr set by hand after reassembling to make sure there are no collisions between the burr sets. Collisions will cause irreparable damage to your burrs and may also damage your motor. Do NOT start your grinder and remove the shim IF you believe your burrs are contacting one another.
3. Grind coffee into your portafilter and draw a shot. Multiple shims will draw the burr sets even closer - BUT BE CAREFUL. One shim was enough to make my grind satisfactory.