# Stone trough my grinder



## iulianato (May 5, 2015)

Hello All,

This morning I had a terifiant sound while grinding for the usual 3rd shot. The plan was to make 5 shots (2 for wife 3 for me) but we only had one each due to a clandestine stone in the bag.

So, the first two shots were fine 18.8g in 38g out in around 42s

The 3rd that had the stone was 18.8g in 30g out in 63s.

Set the grinder two notches back

The 4th 18.8g in aborted at 83s - 10g out

Set the grinder other two notches back and the 5th was similar to 4th.

Now, I'm sure that something happened with the burrs because previously for this bean the grind time for 18.8 g was 6.0s, and quantity drops down for last 60g in hopper but not less than 18g. The grind with the stone ended with 15 g instead of expected 18.x and the next grind, the one for 4th shot, ended (6s) with 13g.

Looking at the pictures I can see that the burrs are affected but I do not understand the effect and I do not understand this behaviour.

Cleaned the burrs and grinding chamber and I'll try again tomorrow but I'll expect the same. I can't see how the cleaning will solve this issue.

Anyone can explain this? Burrs are affected but not too bad I think.


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## El carajillo (Mar 16, 2013)

If yo blow up the photo's on your monitor you will be able to see the damage is considerable. Not only does the large Item cause a severe nick in the burrs but the crushed up particles damage the fine edges on the other teeth. The particles of stone can also damage the wiper arms on the carrier.

You will need a new set of burrs. Examine the lower carrier for nicks or any severe damage. If only tiny nick's / chips you can probably remove these with a fine file.

Afraid there is no other remedy. ALWAYS CHECK BEANS ON A TRAY before putting them in your grinder.

You are not the first and will not be the last to have this problem. Sorry no consolation.


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## Stanic (Dec 12, 2015)

Oh yeah, the burrs have had it I'm afraid









Good advice from El carajillo, I also check the beans when weighting, before grinding, and I've found a stone three times so far.


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## MildredM (Feb 13, 2017)

Rotten luck.

I haven't had one in roasted, but I've had a few in green beans. How carefully do roasters (businesses) check, or are they even able to check?


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## Inspector (Feb 23, 2017)

When i had a couple of stones from the roasted beans i sent an email to the roaster they were offered a bag of beans and a bean storage container free of charge because i told them i was single dosing that time so no burr damage. And they told me they do use a destoner machine but on a very rare occasions couple of stones might still sneak in. From that day on i empty every bag of beans on a tray and check if there are any stones first.





 link for probat destoner


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## Nopapercup (Nov 6, 2016)

Wow I need to start checking for stones!


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## johnealey (May 19, 2014)

Whilst not a replacement for checking beans on a tray pre loading into grinder, how they have been dried as greens will assist in knowing which ones to keep an eye out for. African raised beds stand a lower chance of having stones in than patio dried, although equally can end up with nails / screws and twigs in.

I have a reasonable collection of foreign objects found both before roasting (I run a magnet over all greens and spread out under a bright light on a white background to pick up the odd stone) and roasted (some stones will escape a visual check as could be the same colour and size as a green bean).

The higher the grade of bean the less chance of foreign objects but bear in mind that there is still a chance of something unintended ending up in there. I had some 85 point Cuban Serrano greens recently that were a bit stoney and caught one just as about to tip into the hopper of the R120, so I now move the beans between 2 glasses as a final check.I have no idea how much a set of burrs are for the R120 as cannot see any listed but suspect are in the multi hundreds, hence the extra care!

I do feel for the OP especially as a bank holiday weekend and if hadn't spotted the lido hand grinder in the rear of the picture and only just seeing this, could have offered a loan grinder as not too far away in Coventry ( @iulianato drop me a PM if needed).


​
Luckily the burrs if for a Mazzer (?) are stocked by Bella Barista so may not be too long a wait

John


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## ashcroc (Oct 28, 2016)

Inspector said:


> When i had a couple of stones from the roasted beans i sent an email to the roaster they were offered a bag of beans and a bean storage canister free of charge because i told them i was single dosing that time so no burr damage. And they told me they do use a destoner machine but on a very rare occasions couple of stones might still sneak in. From that day on i empty every bag of beans on a tray and check if there are any stones first.


Think I've guessed how you chose your user name. 

Been a bit lax with checking since I stopped single dosing but think I should be more thorough just in case.


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## iulianato (May 5, 2015)

El carajillo said:


> If yo blow up the photo's on your monitor you will be able to see the damage is considerable. Not only does the large Item cause a severe nick in the burrs but the crushed up particles damage the fine edges on the other teeth. The particles of stone can also damage the wiper arms on the carrier.
> 
> You will need a new set of burrs. Examine the lower carrier for nicks or any severe damage. If only tiny nick's / chips you can probably remove these with a fine file.
> 
> ...


Very much appreciated your input and help offering on pm

The burr carrier and wiper arms are OK. And surely I'll need new burrs.

I used to weight the beans in the large tray that comes with amir scales and inspect them but since I bought the Vesuvius I started to drink more and that became too small so stopped inspecting( I make now 7-8 x 18g - 19g shots in the morning - 3 for my wife 1 for me and 3 to 4 for my keepcup to take at the office; if not a working day I make 4-6 doubles. Before was 5 shot and 3 of them for work) . And never found any odd things.

Now, a lot of coffee is to inspect in the morning so I gave up inspection and started to weight in a plastic jug so not much to detect.

Now I ask myself :Should I think about a way to check the beans quicly OR kerp weighting in the jug and buy 2 burr sets so have one as spare?


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## ashcroc (Oct 28, 2016)

iulianato said:


> Very much appreciated your input and help offering on pm
> 
> The burr carrier and wiper arms are OK. And surely I'll need new burrs.
> 
> ...


Pour whole bag of beans out onto a baking tray or similar then put back in bag once checked? At least then it'd only be one check per bag. Only thing I've ever found was a rogue green that had escaped the roasting process but it's only a matter of time.


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## iulianato (May 5, 2015)

johnealey said:


> Whilst not a replacement for checking beans on a tray pre loading into grinder, how they have been dried as greens will assist in knowing which ones to keep an eye out for. African raised beds stand a lower chance of having stones in than patio dried, although equally can end up with nails / screws and twigs in.
> 
> I have a reasonable collection of foreign objects found both before roasting (I run a magnet over all greens and spread out under a bright light on a white background to pick up the odd stone) and roasted (some stones will escape a visual check as could be the same colour and size as a green bean).
> 
> ...


Very kind of you to offer a loan grinder and should I admit that is very tempting but having the lido, some workout in the morning will be welcomed. Sure I will not be able to pull the brew lever for the 8th shot but I'll be happy that I made 7.


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## iulianato (May 5, 2015)

The OEM burrs are cheap. They are as much as a kg of good coffee.

Now that I have to change them I'm thinking why not going for titanium burrs? But is ti offering grind quality aswell as longevity? Or is just about longevity? Worth an extra hund investment in a £350 grinder that I'll probably move on by the end of the year?


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## johnealey (May 19, 2014)

I would probably hold of on the TiN burrs as they can still be damaged by an errant stone etc.

It's one thing if your grinder is supplied with them (will last a normal lifetime in home use) but I think most people would struggle to taste any difference in the cup compared to say swapping out regular burrs on a much more frequent basis. The benefits of less heat produced by coated burrs / consistency etc are aimed more at cup after cup after cup in a commercial environment. The above is very much based on personal experience in the cup so would treat as is, some can taste the difference guess you would need to taste for yourself blind to see if worth it.

Unless the steel the F64 burrs is made of is particularly soft, then could see the benefit of TiN but only if the cost is less than multiples of std steel burrs if that makes sense.

Assuming the cost of TiN burrs is a couple of hundred then suspect you would get a much better improvement in the cup taking this non spend and the second hand sale of your current grinder and buying something better in the cup.

Some of the domestic aimed grinder such as the Rancilio rocky could definitely have benefited from harder burrs (

It is of course an individual thing but unless you really constrained by size of grinder might be worth looking into the above (plus checking for foreign objects) bearing in mind the more esoteric (and Ceado) grinders that have come onto the market recently are much more house friendly (if not so much wallet!)

John


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