Why it matters
- Two kinds of alignment. Parallelism (burr faces not tilted relative to each other) and concentricity/runout (the burr spinning true on its axis). Misalignment makes one side of the burr produce coarser grounds than the other 18:51. A tilted (co-planar) misalignment acts like a hinge. One side grinds coarse and the other fine, so you get more fines, more boulders and a wider spread. An off-centre (radial) misalignment is a separate problem 2:02.
- It matters more as burrs get bigger and cleaner. The larger the burr and the lower its fines, the more alignment counts 29:33. Multi-purpose burrs, with a tiny aperture and no pre-breaking, need very good alignment. Lance Hedrick puts much of the harshness people blame on SSP burrs down to poor alignment 20:26.
- On a dual-burr grinder, the pre-breaker's alignment hardly matters but the finishing burr's matters a lot 10:44.
- A badly seated upper burr carrier can make espresso impossible even at burr touch, because boulders slip through 32:07.
The marker test, and how Lance Hedrick's view of it changed
Method (2021). Clean the grinder thoroughly first, because one stray fragment throws the result. Draw on the flat land of one burr with a dry-erase marker, reassemble, run the motor and close the burrs slowly until they only just touch, then unplug and look where the ink was wiped. Unwiped areas show where the burrs do not meet 0:00 5:06. Stop at the faintest touch. Going past it or running too long wipes everything and gives a false pass 11:12. Mark the burr and carrier so they go back in the same orientation, and keep the grinder unplugged while working 9:42. Do not try it on burrs without flat lands, such as ghost burrs 0:00.
Fixing it. Lift the burr and slide small aluminium-foil shims (about 6 µm each, folded to about 12) behind it on the side opposite the wiped area, retest, and then check the stationary burr too 8:07. Lance Hedrick expected better sweetness and clarity afterwards 13:47. Budget grinders ship poorly aligned, and foil shimming greatly improved filter results 43:07. Foil or aluminium tape behind the burr, applied evenly, still works on cheap grinders in 2026 19:21.
Growing caveats (2021 to 2026).
- In 2021, a full wipe was better than a half wipe but didn't prove alignment under load 29:41 7:41.
- By 2023 it was helpful but couldn't show what happens under load 20:56. A micrometer or dial indicator with foil shims is more objective 7:38.
- By 2025 he called it a weak check and suggested measuring runout with a dial indicator instead 11:56. Grinding into chirp can give a clean wipe that falsely suggests alignment 9:09 20:26. Marker and shims aren't a full fix. True alignment also needs precise threads and a wobble-free shaft, and springs can let the burr move under bean load 8:39. An off-centre burr matters more than a less-than-perfect wipe 10:10.
- In 2026 his view was that no static test shows alignment under load 20:22.
Better measurements
- Dial indicator. Lance Hedrick shimmed an EK43's rotating carrier to about 1 µm of runout, which he thinks is rare 14:43. He also checked a Kopi Deva shaft, within about 0.05 mm 32:11, a Timemore 078 at about ±2 µm 0:00, and a Kafatek Monolith Max 2 that was excellent out of the box 18:19.
- Lock-to-chirp distance. Compare how far the dial travels from burr lock to first chirp before and after a change. A smaller gap suggests better alignment (about 2 ticks on his M98V) 20:55. Zerno's designer targets 20 to 30 µm 1:31. On the Lagom 01, pressing on the hopper changes the reading, so measure gently 32:08.
Design beats tolerance
- Tight tolerances and expensive machining alone don't guarantee alignment. How the parts are designed to locate each other, and how the final alignment is set, matter more 12:12 12:12 21:57. Weber's kinematic design is his example, and he advises testing before shimming grinders like it 21:42.
- Factory torque specs on burr and auger screws help keep alignment 27:21.
- Some faults can't be shimmed out. An EK43 with a bent drive rod showed about 60 µm of play and couldn't build pressure even at chirp 8:36.
- Swapping plastic burr plates for metal (on a Baratza Vario, for example) can help 21:57, and engineered alignment made the Vario and Forte modding favourites 0:30.
Hand grinders
- A burr fixed to the axle with several bearings gives repeatable settings after disassembly, while a push-fit burr sits slightly differently every time 8:45. Fixed burrs give better alignment, distribution and consistency than floating ones 7:07 17:21. Lance Hedrick calls a fixed burr a must above about $100 7:03, and floating is acceptable below that 17:21.
- A short axle with triple bearings flexes less under load 5:04.
- Fitting burrs yourself in a hand grinder risks centring errors, and factory-fitted burrs tend to do better 12:07.
Why stated microns per click are approximate
Burr-gap figures assume perfect alignment, which no grinder has, so vertical burr travel is the more objective number 9:27 38:52. See zero point and grinder scales.
James Hoffmann's view
- Heavy burr wobble made a portable Lume grinder's output very uneven 4:17. Play in a Hario Slim's shaft means poor alignment and a poor grind 1:00.
- The EK43 has historically needed alignment work to avoid wobble and an inconsistent grind, which is frustrating at its price. Well-aligned units make very good coffee 12:40.
- On the Weber Key, a long moving-burr shaft not stabilised near the burr could let small shaft movements affect alignment over time 6:39.
Daddy Got Coffee's view
- Flat burrs that aren't parallel make bigger particles where the gap is wider. A few microns matter, especially for espresso 4:39 6:41 14:24.
- Daddy Got Coffee checks with a marker wipe and the chirp-to-lock distance (Mazzer specifies 10 to 20 µm) 7:11 5:39. He measured a Zerno Z1 at 5 to 15 µm, a Mazzer Philos at 15 to 18 µm and a Lagom P80 at about 15 µm 0:30 0:31 12:27.
- On a Bentwood, though, improving from about 40 to 15 µm made no difference he could taste 10:20. Poor factory alignment on a Timemore 078S did cause severe channelling until it was fixed 5:42.
- Grounds left behind the burrs during reassembly throw alignment out 8:11. Conicals have several alignment axes and DIY realignment often makes things worse 16:24 17:27.
Kyle Rowsell's view
- Flat-burr grinders often still need aligning even when they arrive in reasonable shape 10:13. A tidy build on his DF83 did not mean the burrs sat true, and that unit needed work before it performed at its best 8:12.
- Construction helps, which matches Lance Hedrick's "design beats tolerance" point. Original Varios drifted out of true with use, and a stiff metal burr chamber keeps things steadier 2:40. The DF64P and DF64E swapped springs and loose clearances for a bolted chamber, which improved alignment from the factory, though individual units still differ 2:33.
- Kyle Rowsell's Lagom P64 came well aligned while his original DF64 needed manual shimming and printed parts 11:42. Option-O's claim that its grinders need no alignment had held up on the ones he owned in 2023 11:46.
The Coffee Chronicler's view
- In a 2022 test, flat burrs with espresso-style geometry or less-than-perfect alignment could lose to a 1Zpresso ZP6 in the cup even though they sieved more evenly 18:28.
- On the 2025 Timemore Sculptors, shimming the burrs into alignment is slow work, so he would not plan on swapping burr sets often 3:04.
Sprometheus's view
- A marker test on a Niche Duo showed both burr sets brushing slightly more on one side. It was too little to affect the cup, and a shim would correct it 3:43. Like Daddy Got Coffee's Bentwood result, a small measured error did not show up in taste.
- The DF83V's spring-held carrier looked like an alignment risk, but the one Sprometheus tested was true with both burr sets 5:28.
- Shims also set the finest reachable grind. On the Baratza Encore ESP Pro, units shipped with different shim counts behave differently at the same dial number 7:06.
Brian Quan's view
- In a talk with Denis Basaric of Kafatek, Brian Quan heard that flat burrs must sit parallel and an error of around 50 µm is noticeable. Conical burrs need to be concentric but tolerate error better 11:18. That agrees with Lance Hedrick and Daddy Got Coffee that flats are the more sensitive type.
- On a JT64 the loose tolerances let the burrs chirp when he pressed on the chute, so he re-checks alignment after every reassembly 17:00.
For Notchbook
After shimming, re-seating or swapping burrs, the zero point and the effective grind both move. Treat it like a new grinder. Find zero again and dial in again instead of trusting earlier pinned settings.
Summarised in our own words from the creators' videos, with every point linked to the moment it comes from. Notchbook isn't affiliated with or endorsed by any of these creators, so please watch the originals for full context. Sources
Keep reading
- Astringency
- Conical vs flat, and burr geometry
- Grind size and extraction
- Particle size distribution and fines
- Retention, static and RDT
- Seasoning new burrs
- Slow feeding and RPM
- Zero point and grinder scales
- Grinder workflow: single dosing, WDT, RDT, purging and storing beans
- Troubleshooting: what to change when a cup tastes wrong
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