Aillio Bullet Maintenance: Drum Shims

An often-overlooked and under-appreciated part…

Like all other great coffee roasters, the Aillio Bullet requires routine maintenance and care if you want it to function properly and last a long time. This mostly amounts to a lot of cleaning, but there will be times where you’ll need to replace a few parts or give your roaster a bit of a tune-up. Many Bullet owners will be familiar with parts like the IBTS Fan, the Cooling Basket Filter, or others which are commonly replaced. In this article, we want to focus on a part that we feel doesn’t get the attention it deserves—The Drum Shim(s).

Two Problems That Shims Might Address

Drum shims help to control the horizontal position of the roasting drum, so it’s no surprise that the two main issues that can be resolved with shims are related to drum spacing. The most common issue involves coffee beans falling out of the drum mid-roast, and this is caused by the gap between the drum’s edge and the front faceplate being too wide. You can also have the opposite issue where that same gap isn’t wide enough, which can result in varying levels of scraping as the drum’s edge rubs against the front faceplate.

So why do we say that drum shims might address these problems? The truth is there may be other factors at play, and it’s best to resolve these first before playing with the shims. If you’re experiencing one of these issues, you should start by checking the position of the drum, which can be done by pressing on the front bearing/shaft. This should cause the shaft to shift back about 1mm in depth, but the shaft should pop right back into place if the drum is in the correct position.

If the drum doesn’t pop back, then you’re likely dealing with a pulley system issue that drum shims won’t directly resolve. With our focus set on drum shims, we won’t get into the details of aligning the pulley, but Aillio provides helpful guidance on this topic on page 27 of the operation manual. Assuming your drum is correctly positioned, please read on!

Locating The Drum Shims

You can find the drum shims mounted on the drum shaft just behind the front bearing. By default, Bullets come pre-installed with two drum shims of differing thicknesses.

Accessing the drum shims involves removing the front faceplate off of your Bullet. Sounds a lot scarier than it actually is! The video below demonstrates this process pretty well (from 0:00 – 1:10). Don’t be alarmed if the shim depicted in the video appears to be far thicker than the ones installed on your roaster.

You shouldn’t need anything more than what is included in your Aillio tool kit for this job, but a pair of needle nose pliers will help you out when disconnecting some of the wires on the control board. It’s also a good idea to take reference pictures as you disassemble the front of your roaster. This should save you a headache during reassembly.

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Using Drum Shims To Your Advantage

As we mentioned earlier, the role of the drum shim is to control the spacing between the drum’s edge and the front faceplate. Ideally, this gap should be 1mm wide. Each shim added/removed to the drum shaft contributes to the overall width of this gap. For this reason, it’s important to pay attention to the number of shims you’re planning to add/remove to your drum and the thickness of each.

More/Thicker Shims = Larger Gap

Less/Thinner Shims = Smaller Gap

To reiterate—If the gap is too wide, you run the risk of coffee beans slipping through during roasting and causing a ruckus. If the gap isn’t wide enough, the drum can scrape against the front faceplate. No good!

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Sourcing Shims

We have sold Aillio’s shims set on our website for a while now, but we don’t plan to offer them for much longer due to high costs. Instead, our goal is to provide you with enough information here so you can go out and purchase a few shims from your local hardware store at what will hopefully be a fraction of the price.

Each shim has an internal diameter of 10 mm, and an exterior diameter of 16mm. Aillio’s shim set comes with 5 shims in total of varying thicknesses: 0.5mm, 0.6mm, 0.8mm, 1mm, and 2mm. You don’t need to get shims of these exact thicknesses, but the varietyA botanical variety is a rank in the taxonomic hierarchy below the rank of species and subspecies and above the rank of form (form / variety / subspecies... ...more can be helpful for managing the drum gap with precision. They are made of stainless steel.

It’s also worth noting that the Aillio tool kit that comes with each Bullet roaster includes a couple of spare shims, meaning a trip to your local hardware store may not even be necessary.

No Problems? No worries.

Of course, if you aren’t experiencing any issues related to drum spacing, then there’s no real need to fuss with drum shims. It’s a good idea to check on the gap between the drum and the front faceplate every once in a while, maybe after you wrap up a session of routine maintenance/cleaning. If you do notice an issue, now you have an idea of what may be the cause!

Still unsure? Send us an email at [email protected] and we’ll do our best to help.

Looking for other Bullet parts? Check out our standard parts list for common parts and our extended parts list for less common and/or more technical parts.