# Finding a grinder - DIY?



## harrymerckel (May 9, 2020)

I'm new to the world of espresso, currently trying to learn as much as I can and work out how to reliably and repeatedly make something that tastes great.

From what I've seen, one of the most important parts of making good espresso is the grinder.

I currently have a Krups 'Expert' GVX2, which I know is not a good grinder for espresso - it's fine for Aeropress, as I've been using it for the last year or so, but I know it's not precise enough or consistent enough at the finer end to work well making espresso. I also have a dirt cheap ceramic conical burr grinder, which might be a little better but certainly isn't a good long term solution.

Many people seem to like the Niche Zero at what seems to be the mid-range at about £500, but I'd rather not spend more than about £100 right now - after all, my espresso machine was around £100. I've seen things like the Sage SGP at around that, but I was wondering if I could modify my bad grinder or build something myself that would beat that.

I have CAD experience, a well tuned 3D printer, a shed full of assorted DIY tools, a box of assorted electric motors, electronics tools and experience and (after lockdown is over) access to a CNC mill and possibly a small waterjet cutter. I will, relatively soon, have a few weeks downtime during lockdown where I can tinker 'full time'.

My real questions:



Can I adjust / modify my Krups grinder to be a little more suitable for espresso? I'm happy to do pretty much anything to it, I've seen shim mods for some other grinders but can't see much on that one. Can you replace the 'burrs' with something decent, or are there huge flaws with the whole mechanism?


Should I buy something at around £100 or go and build my own? How difficult might that be?


If I'm going to build my own, are there any designs around? What specifications should I be aiming for?


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## HDAV (Dec 28, 2012)

I have seen pics of some prototype grinders with 3D printed parts, there are bargains to be had especially if you fix and repair an existing unit like an ex commercial machine like a Mazzer etc there are some mods to some basic machines like the Gaggia mdf.

i dont know anything about the internals of the krups but not sure how feasible replacing the burrs would be.


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## allikat (Jan 27, 2020)

It'd be a big project to make your own, even if you can make it with a 3d printer. First you'd need a set of good burrs. The ones in your current Krupps grinder are the lowest end of actual burr grinders, the big breaker blocks produce a huge amount of fines. Decent ones start at around 20-25 quid. Then you'd need a motor capable of spinning those burrs or a gearbox to provide enough torque to make them turn with beans in the way. You could motorise the small ceramic perhaps.

I did shim my severin grinder to do something close to espresso grind. I just took the top burr off, and added some aluminium tape to the back of the burr. But do be aware that the tolerances are pretty loose at that price point, and getting good espresso grind needs consistent particle size. An excess of fines will end up with some in the cup making a silty drink.

The usual answer to the budget grinder question is a used commercial machine. I got a Compak k6 for 65 quid, a new hopper was 30 pounds, new burrs £25 and some food safe grease for a tenner. A few brass brushes and that made it go fine. Keep an eye on fleabay, gumtree and so on for them. Make sure to see them work in person if possible, it shouldn't make any odd screeching or grinding noises when run empty. Look for San Marco, Compak, Macap, Mazzer, Eureka or Ceado. Many of those make grinders for others to badge, so ask if in doubt.


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## harrymerckel (May 9, 2020)

allikat said:


> -snip-


 Great, thanks for the information - I'll see what I can do then, but it seems like I'd be better off getting a cheap commercial or similar unit like you suggest, then later thinking about building my own when I've had a chance to properly learn how it all works.

I'm currently looking at the Iberital MC2, most likely new at that price point, and I've saved a few eBay searches for popular brands I've found mentioned a lot here on the forums.

With the ceramic grinder I'd be concerned about wearing things out too fast by driving it under power, it's not exactly well engineered and it already feels like it wants to fall apart in my hands. It was absurdly cheap though... I might still try some kind of worm drive assembly, I have a number of old RC car motors that should be suitable when geared down to somewhere around 200 RPM. If that works it'll be a good step towards building something from scratch.

Having partially opened up the Krups it's a relatively simple construction, potentially with room to 3D print better plastic parts to make adjustments easier, but I don't hold much hope given how bad the burrs are. They have an OD of 40mm, which from looking around doesn't seem at all standard and much smaller than most grinders. The top burr locking mechanism and adjustment system is all plastic and has a fair amount of flex to it, so that might be an angle of attack for improving it a little. The grind adjuster dial is artificially limited to the big discrete steps, although I suspect that mechanism helps it not slip during operation. I'll probably end up just keeping it for Aeropress coffee, especially if the MC2 is as painful to adjust by large amounts as people suggest.


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## Rob1 (Apr 9, 2015)

Have a look at the OE Pharos and Mahlgut teardown videos for ideas on how to build your own. It can be quite simple if you have the precision tools and sheets of metal.


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## allikat (Jan 27, 2020)

The principle is very, very simple. The mechanics and design are the tricky bit. The tolerances are very fine, and turning burrs at that kind of tight gap with beans in the way (which is the point) will take a lot of force. The bigger the burr, the better the result, but also the higher the power need because those beans and grinds spend more time in those burrs "slowly" getting cut down to the desired size. Low end burrs do a lot of smashing of the beans to quickly get them into the rough size range for the rest of the burr to grind it down, that makes a lot of dust which are known as fines, which are grounds way too small for any real use and those often cause issues like bitter taste in the cup and silt.

If the plastic you work with has any significant flex, it will move under the strains imposed by grinding the beans. However that doesn't stop you taking a busted up ex-commercial unit with a good core and rehoming it in a custom 3d printed case. Hoppers, grind chutes, portafilter holders are all great choices for 3d printing. Just be aware that coffee grounds stick very easily and anything in contact with them should be super smooth. Look at the Ceado E37 Naked or hero for an example of what could be done with any good motor and burr set.


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## Northern_Monkey (Sep 11, 2018)

@harrymerckel - I reckon trying the shim mod might get you the furthest with your current grinder. Modifying it for other burrs is going to be very hard to give you something that is better.

I've seen some posts on really neat motorised mounts for hand grinders similar to the one on page 9 of this HB thread.

Unless you are an engineer with a full machine shop already you would be hard pushed to make one accurately enough or to a £100 budget. Some people have made them from scratch and they look amazing, but likely cost more than the commercial equivalent.

Maybe get a hand grinder and give it a try?

https://www.home-barista.com/grinders/motorized-hg-1-with-various-speed-t53547.html


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## harrymerckel (May 9, 2020)

@Northern_Monkey Wow, that one looks fantastic - I have enough equipment here to perhaps make an adapter for a hand drill, and something the one in the picture wouldn't be off the table after I get back to the workshop. I'd probably want to get a better hand grinder that I'd actually trust not to fall apart after a little use, but I'll leave that approach for now.

I'll give the shim mod a go, I now have my espresso machine and have found that the second finest grind setting hugely under-extracts. I might experiment with the pressurised basket, but I know that's not the best way to go for the best coffee.

I'm now trying my cheap hand grinder, have so far made an absurdly sour shot that extracted far too fast, then one that choked - I'll keep trying, currently using some cheap decaf beans but when I get somewhere close to drinkable I should be able to swap to something better with some confidence that I won't completely waste it. Is there a particular physical size I should be aiming for, or an easy way to tell that it won't work before trying to pull a shot, or is it all down to experience?

I should probably also make some tools like those on the right of that image, so far I've just been using a cocktail stick to redistribute the grounds and a finger to get it relatively flat before tamping.

@allikat Thanks, and yes I can see now that it's probably not feasible to do much beyond repairing and modifying an existing unit until I have access to precision tools again, at least for the mechanically important parts. I've already 3D printed a tamper, which seems to do the job and is much nicer than the little plastic one the machine came with, and I'm currently looking at designs for things like distribution tools. I suspect I'll use 3D printing more as a prototyping tool, before machining something nicer later.

@Rob1 The OE Pharos looks fantastic, and should be entirely possible to replicate (or at least create something similar) with a waterjet cutter and off the shelf parts. Thanks!


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## t8by (Apr 17, 2020)

@*allikat*

*Do you know if there is a list somewhere of all of the brands which are rebadged Compak grinders?*


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