When and How to Replace Coffee Grinder Burrs: Signs to Look For

Worn burrs almost never announce themselves. There's no warning light, no obvious failure, no moment where the grinder stops working. What happens instead is much harder to spot: the coffee gets very slightly worse, very slowly, over several months.

By the time it's noticeable, most people have already adjusted around it. Ground a bit finer. Nudged the dose. Accepted that dialling in takes longer than it used to. Then a fresh set of burrs goes in and the difference is obvious immediately.

This guide covers how to know when you're getting close, which symptoms actually point to burr wear rather than something else, and what's involved in changing them.

Why Burrs Wear at All

Coffee is more abrasive than it looks. Every bean that passes between the burrs takes a tiny amount of metal with it. Multiply that by tens of thousands of doses and the cutting edges gradually lose their sharpness and definition.

That's normal wear, and it's predictable. What isn't predictable is damage. Small stones, staples, packaging fragments and other foreign objects occasionally make it into a hopper, and a single one can chip a burr in a way that months of ordinary service wouldn't.

Sustained heat and running the grinder empty for long periods don't help either. But for most commercial sites, the main factor is simply volume.

The Most Reliable Measure: Kilos, Not Months

This is the single most useful thing to take away.

Burr life should be tracked by how much coffee has passed through the grinder, not by how long the grinder has been installed.

A café doing 15kg a week and a café doing 4kg a week will be on completely different replacement schedules, even with identical machines. Time-based intervals just don't work.

As a general guide for the Macap Supra range:

• 68mm hardened steel burrs — around 600–800kg
• 83mm hardened steel burrs — around 800–1,000kg
• 68mm titanium-coated burrs — around 1,200–1,400kg

Larger burrs generally last longer, because the work is spread across more cutting surface. Titanium coating extends life significantly again, which is why it's worth considering on high-throughput sites.

Working out where you sit is straightforward. Take your average doses per day, multiply by your dose weight, and multiply by your trading days. A site pulling 300 doses a day at 18g is grinding roughly 5.4kg daily — so a 68mm set could be due somewhere around the four-to-five month mark.

That maths takes five minutes and tells you more than any symptom on the list below.

Signs to Look For

If you're not tracking kilos, these are the things that tend to show up first. Individually, none of them proves burr wear. Several together usually do.

1. Grinding is taking longer

Your grind time creeps up for the same dose.

Worn burrs cut less efficiently, so productivity drops. On a busy bar this is often the first thing anyone actually notices, because it starts affecting service pace.

2. You keep grinding finer to hit the same shot

This is the clearest single indicator.

If your grind setting has been drifting steadily finer over weeks or months to maintain the same extraction time – with the same coffee, at the same age – the burrs are almost certainly losing their edge.

Worth noting the direction of travel here. A new coffee needing a different setting is normal. A continuous one-way drift is not.

3. Shots have become harder to dial in

Extraction times get less predictable. Two shots at the same setting behave differently.

Worn burrs produce a wider, less controlled particle distribution, which makes the puck less consistent and channelling more likely. You end up chasing the grinder rather than adjusting it.

4. The cup loses definition

This one is subjective, but it's real.

Coffee from worn burrs often tastes flatter and less distinct. Sweetness fades, acidity loses its shape, and there's frequently a dry or slightly bitter finish that wasn't there before.

Baristas often describe it as the coffee sounding muddy rather than defined.

5. More fines, more clumping

You start seeing more clumping in the portafilter and more dust around the grinder.

Distribution gets messier and needs more intervention before tamping.

6. The grinder sounds different

A change in tone – harsher, rougher, or noticeably louder under load – is worth investigating.

If it's a sharp metallic sound, stop and inspect. That can indicate a foreign object or burrs making contact with each other.

7. Visible wear on the cutting edges

Sharp burrs have crisp, defined edges. Worn burrs look rounded, polished or slightly shiny along the cutting surfaces.

Chips, nicks or uneven wear across the face are clear replacement signals regardless of how much coffee has gone through.

On the Supra range, the Fast Opening System gives you tool-free access to the burrs and grind chamber, so having a look takes a minute or two rather than a workshop visit. That makes routine inspection realistic – which is exactly the point of it.

Before You Blame the Burrs

Plenty of these symptoms have other explanations, and it's worth ruling them out first.

Coffee freshness. Very fresh coffee behaves differently from rested coffee. So does coffee that's gone stale.

A dirty grind chamber. Old oils and coffee residue build up and affect grind flow and taste considerably. A proper clean solves a surprising number of problems that look like wear.

Alignment or loose components. If the burr carrier or retaining screws have worked loose, you'll get inconsistency that has nothing to do with sharpness.

The espresso machine. Temperature stability, pressure and group cleanliness all affect the cup and are easy to misattribute to the grinder.

Water. Changes in filtration or scale build-up shift extraction more than most people expect.

My rule of thumb: clean thoroughly first, then assess. If the symptoms survive a deep clean and your grind setting has been drifting one way for weeks, you're looking at burrs.

How to Replace Grinder Burrs

The process varies by model, so treat this as what's involved rather than a set of instructions for a specific grinder. Always work from your model's documentation, and if your grinder needs recalibration afterwards, get a technician to do it.

1. Record your current grind setting. Before you touch anything. On grinders with a zero-point adjustment ring, note the reading – it makes getting back to a workable starting point far quicker.

2. Isolate the machine. Switch off and unplug. Not optional.

3. Empty and remove the hopper. Then run off or vacuum out any coffee left in the chamber.

4. Open the grind chamber. On the Supra range the Fast Opening System handles this without tools. Other models will need the appropriate tooling.

5. Remove the old burrs. Keep the screws safe and note how everything sits. Burr sets have a specific orientation, and some have alignment features that need to seat correctly.

6. Clean the seats thoroughly. This matters more than people think. Any coffee residue or debris under a new burr will throw off alignment and undo the whole job.

7. Fit the new set. Always replace both burrs together, never one. They wear as a matched pair, and mixing new with used gives you the worst of both.

8. Tighten evenly to the specified torque. Work around the fixings progressively rather than fully tightening one at a time.

9. Reset your zero point and re-dial in. Expect your old setting to be wrong. New burrs are sharper and cut more efficiently, so you'll typically be starting coarser than before.

10. Allow for a break-in period. Fresh burrs season slightly over their first kilo or two, and the grind can shift as they do. Check your shots more often than usual during that period rather than assuming the first dial-in will hold.

Use genuine burrs specified for your model. Your Macap dealer or the REPA network can supply official spare parts, and fitting the correct set matters – burr geometry is engineered for a specific grinder, and a generic equivalent isn't the same component.