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Thread: Cunill Grinder misaligned burrs

  1. #1
    Senior Member robusto's Avatar
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    Cunill Grinder misaligned burrs

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    A few years ago I bought a used Cunill Space grinder, with the intention of replacing the burrs as a priority. That never happened, mainly because I was not confident of buying the right ones online, and the thought of trying to undo the nut which holds the bottom burr onto the motor shaft kinda scared me.

    But I carried on with periodic maintenance, removing the top burr carrier, wiping off the embedded grounds from everywhere that could be reached.

    Under the sweeper plate was always impossible without removing the bottom burr.

    Well, yesterday I tackled the task. I wedged a short length of steel in the chute so it wedged against the steel sweeper. I attached a socket and wrench...and to my pleasant surprise, the nut came off without undue force or drama.

    So a thorough clean of every surface which comes into contact with coffee was finally possible. My fingers still smell from the years of built up coffee gunk.

    But when I went to replace everything, I noticed that the top and bottom plates now touched in one spot.

    In orther words, they are not sitting dead parallel.

    In the very beginning I placed two opposing marks which told me the burrs were on the threshold of touching. But now they touched well before those marks came together.

    After removing/replacing the assembly a dozen times, that was still the case.

    The sweeper plate on which the bottom burr sits is stlghtly buckled. How slight? It must be dead set flat otherwise kiss fine grinding goodbye.

    Some attempts to straighten it with my garage equipment have had moderate success, but to grind finer means the burrs will touch and that cannot be allowed. Maybe the motor shaft is also not precisely 90° perpendicular to the plates.

    Maybe time for a new grinder...unless my dogged perseverance comes to the fore.

  2. #2
    Senior Member robusto's Avatar
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    After five minutes of deep thought, I've opted for dogged perseverance. I'm going to try yet again to fix this trusty grinder. If the alignment problem is solved, I will then buy new burrs.

    So I will then have a great grinder with 59 mm burrs, spinning at 1300 rpm driven by a 445 watt motor, all for under $50...versus several hundred $ to a thousand for a new grinder.

    At the moment I have tools and grinder bits all over the sink and two kitchen benches.

    From the McIver school of invention I made a "dial gauge" to check runout. It's a steel ruler which straddles the top of the grinder chamber, with a small skewer at right angles to it and held on by a small g-clamp. I set the skewer depth until it just touched the wonky sweeper plate.
    [img] dialgauge.jpg[/img]


    Gently turning the sweeper by hand confirmed there is a high side. Now, I would have thought that the 30 mm x 6 mm washer on top of the plate would would iron out any minuscule deflection when the nut on the motor shaft is tightened against it and the burr. Not so.

    So I will have to experiment here, perhaps some paper shims on one side of the stationary adjustable burr? We'll see.
    Attached Images Attached Images

  3. #3
    Senior Member robusto's Avatar
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    Sometimes perseverance is a pain. Last night, I spent several hours slaving over a hot bench attacking this grinder. Tools everywhere, and the more I persevered, the more tools accumulated. Ever seen those TV shows where someone builds a robot in their basement. Not a speck of dirt on the floor, no sawdust over the tools hanging on the walls. No welding torches, no bits of metal offcuts, no metal saws, grinders.....just the robot, a spanner and a screwdriver. Gees I'm envious.

    Anyway, the defacto dial gauge was unwieldly, so into the workshop to fabricate a length of wood which replaced the ruler which was somewhat difficult to hold on edge across the top of the grinding chamber. And a drilled hole through it to take a bolt which could be screwed down to just touch the rotating bottom burr.

    OK, so there is a high spot. What about a little cardboard shim on the opposite side to compensate. Nope, too thick. A piece of paper from a bank statement perhaps? Too thick as well. Hmm. Ah, a bit of aluminium foil. More inert than absorbent paper as well.

    Nope, too thin. Two bits. Three bits. Promising, but now the high spot moved. So we move the aluminium shims around.

    So, this went on for hours and hours. All I succeeded in doing was moving the high spot around. Even did a little panel beating on the sweeper plate on which everything sits.

    Late at night I thought I'd test the grind, with a stone-cold coffee machine. Well, it was a gusher. A few seconds and the cup filled.

    Today, tackled the sweeper plate with my trusty mechanical press again as best I could, spreading the force with a thick piece of steel, and tried again.

    Still a confounded high spot, with just enough space to slide what was left of the bank statement paper under the "dial gauge" bolt on the low side. About 0.0015 inches with the feeler gauge. A bit more shimming here and there and I decided that was as good as it gets.

    Put everything back together, and ground a shot one notch from zero point, in the usual 20 seconds. Twenty seconds = 20 grams.

    Conclusion: Didn't quite fill the basket. Later tonight I'll weigh it to confirm. Extraction: still a tad fast. Taste: very good, but could be better.

    I'll order a new set of grinder burrs and see what happens...

  4. #4
    Senior Member robusto's Avatar
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    The new burrs have been ordered from coffee parts. They are 59 mm diameter flats, and should arrive tomorrow for immediate installation.

    No matter how many hours I put in trying to make the burrs turn 100% horizontal, it will not happen.

    Everything sits on a ridiculously narrow "ledge" cut into the motor armature, just a couple of millimeters wide.

    Despite the potential risk, I've toyed with depositing a thin layer of lead solder on the bottom of the sweeper plate and then filing it so it will sit squarely on this ledge.. perhaps silver solder though the higher temperature may cause further distortion Dunno.

    Acidic food like coffee grinds and lead don't make a healthy recipe. On the other hand, the contact area would be extremely --extremely--small.

    See how the new burrs perform. At least now, even with the old burrs, I can choke the extraction to almost 2 minutes, so that is promising for the new burrs.

    Stay turned.

  5. #5
    Senior Member artman's Avatar
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    Even if you get the bottom burr spot on "level", you would need to make sure the top burr is also dead flat/parallel otherwise you will have a variable gap around the circumference of the burrs. Not sure what that tolerance is for these measurements, it would make sense for an acceptable tolerance (talking fractions of mm) to exist as it would be next to impossible to have both burrs completely flat/aligned?

    Cheers

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    I really think you should contact the Cunill importer in Sydney. I gather from the first post above that all was ok with the grinder until you disassembled it. To my mind partial shimming (or any shimming for that matter) as you described shouldnt be required for it to run true with a simple replacement of plates. There will be some detail that you've missed.

    Call the importer and cut to the chase as you are otherwise just chasing your tail round....

    HTH
    Attilio
    very first CS site sponsor

  7. #7
    Senior Member Yelta's Avatar
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    Have you considered the possibility that you may have bent the shaft when undoing the nut holding the bottom burr?

  8. #8
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    I've had a Cunill Tranquilo (different model to yours but possibly similar) for 10 years. It's now been replaced with a Mazzer. A couple of years ago, I pulled it apart to give it a good clean and when I reassembled it, the burrs were slightly misaligned. Since there wasn't anything obvious that I'd done wrong, I just pulled it back apart and reassembled (exactly as before) and it was fine the second time.

    I never did find out why, but it would seem that there is a possibility for this happening. I note that you've carried this out several times so perhaps it's not the same issue.

  9. #9
    Senior Member robusto's Avatar
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    Paul, I have placed markings on all the removable, rotatable components, and tried reassembling them varying degrees from each other, but alas, to no avail.

    Anyway, the new burrs arrived.

    They look a dull metallic grey, with no shiny spots--which is how I've read new burrs should look.

    Running my finger against them, they felt noticeably sharper than the old ones.

    I'll use the grinder a little later....Unfortunately very few roasted beans left, and yesterday's batch is a tad too fresh.

    Havne't quite got the hang of posting pictures on this new format, so I'll practise that too in the meantime.

  10. #10
    Senior Member robusto's Avatar
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    Quote Originally Posted by Fresh_Coffee View Post
    I really think you should contact the Cunill importer in Sydney. I gather from the first post above that all was ok with the grinder until you disassembled it. To my mind partial shimming (or any shimming for that matter) as you described shouldnt be required for it to run true with a simple replacement of plates. There will be some detail that you've missed.

    Call the importer and cut to the chase as you are otherwise just chasing your tail round....

    HTH
    Attilio
    very first CS site sponsor
    Thanks, Attilio. Very hard to know if the alignment was good before the dissassembly, as I never had the burrs touching in use, of course. But I'm leaning towards your conclusion too that shimming should not be necessary.

    [QUOTE=Yelta Have you considered the possibility that you may have bent the shaft when undoing the nut holding the bottom burr?]

    Yes, I have considered that, but the motor shaft is very rubust and would have taken more effort than I coulld have delivered undoing the nut, to bend it. Hard to tell without a dial gauge.

  11. #11
    Senior Member robusto's Avatar
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    Here's a couple of pics of the new burrs On the left is the new bottom bur, to the right the old one.
    The second picture has both new ones with an old one in the middle.

    The big black washer in the old burr is a just that, a washer which goes under the nut which holds it down.
    Attached Images Attached Images

  12. #12
    Senior Member robusto's Avatar
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    The moment of truth came, making the nightly coffees. Probably 10 grams each of 6 day old beans and ones roasted yesterday.

    I set the coarseness about 4 notches from just touching, and away we went.

    Ground for 20 seconds which normally yields 20 grams. Weighed the grounds and found I had a whopping 27 grams.

    Right away I'm starting to like these new and burrs.

    Brew time took forever. Almost 2 minutes. Obviously--I had a laugh--a much coarser grind is called for.

  13. #13
    Senior Member Yelta's Avatar
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    Sounds like things are looking up.

    Bit like a TV series, looking forward to the next episode, you certainly know how to string things out.

  14. #14
    Senior Member robusto's Avatar
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    Quote Originally Posted by Yelta View Post
    Sounds like things are looking up.

    Bit like a TV series, looking forward to the next episode, you certainly know how to string things out.
    I had a laugh Yelta. Hopefully this is unlike those annoying TV soaps. Trying not be, anyway.

    We'll see how it handles the 2-day-old roast beans at breakfast tomorrow morning.

  15. #15
    Senior Member robusto's Avatar
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    Once again, I'm running out of rested beans to do the tweaking I want. The grind time is amazingly different with these new burrs. From 20 seconds for 20 grams, I reduced this to 15 seconds and I'm still getting way over: 24 grams. I'll aim for a 12 second grind and see what happens.

    I've made the grind two notches finer, yielding a 22-second extraction. I'll go finer still to get 25 seconds.

    Coffee OK, but a tad bitter, but reluctant to do a longer cooling flush until I iron out the grind.

  16. #16
    Senior Member Yelta's Avatar
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    Quote Originally Posted by robusto View Post
    Once again, I'm running out of rested beans to do the tweaking I want. The grind time is amazingly different with these new burrs. From 20 seconds for 20 grams, I reduced this to 15 seconds and I'm still getting way over: 24 grams. I'll aim for a 12 second grind and see what happens.

    I've made the grind two notches finer, yielding a 22-second extraction. I'll go finer still to get 25 seconds.

    Coffee OK, but a tad bitter, but reluctant to do a longer cooling flush until I iron out the grind.
    Three days mate! what's happening? I'm hanging out for the next episode.

  17. #17
    Senior Member robusto's Avatar
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    Yelta, I'm waiting for my beans to age.

    Until I can get a batch of stable, aged beans there is too much fiddling with the grind, and the taste will still be wrong.

    But the most surprising thing so far is that instead of taking 20 seconds to grind 20 grams, it now takes just 10.

    Using a timer, as I always have done to grind, I am able to consistently get those 20 grams. So, that variable is eliminated.

    The main variables left would appear to be the ground particle size, and maybe the brew temperature.

    I will update in depth as things progress.

  18. #18
    Senior Member robusto's Avatar
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    We've been away for a few days, but that's allowed our roasted beans to well and truly degass, probably at point where immediate consumption would be be optimal.

    So today, I ground for 11 seconds and got 22 grams of grinds in the basket. For the sake of consistency, I leveled off 2 grams.

    The extraction took 27 seconds.

    I time it from the moment I hit the touchpad. For that is when low-pressure water emerges from the shower screen momentarily. The 3-way valve then opens to release the pressure build up.

    The valve then closes and the full 9 bar pressure saturates the grinds. Yes, electronic pre-infusion.

    Taste was was very good. No bitterness, perhaps a note of sourness.

    I am leaning towards perhaps 22 grams in the basket in future for a more intense extraction.

    There are so many other variables to play with and eliminate.

    Temperate is one, but I am thinking the Grimac group which I used to think ran hot, may be just about right with no major cooling flush.

    See how we go.

  19. #19
    Senior Member robusto's Avatar
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    This is a very turgid process, and while I may aim for consistency, achieving it is proving more difficult. Grind setting now has to be altered much more often than used to be the case. Before the alignment and with the old burrs, adjustment was to cater for newish versus oldish beans, within a parameter I was familiar and comfortable with.

    Now it is all that, and more. For instance, last night I poured a niceish shot in 30 seconds. This morning, with the same settings, it blew through in 18 seconds.

    Grinding 2 clicks finer, I stretched that back to 30 seconds, and the taste was radically different. Of course. Much sweeter, more oily.

    Will I get the same result tonight? That is the frustrating part. I am not confident I will.

    The only way to really do it is to keep feeding cups down the sink, and grinds into the bin.

    In the quest for perfection, I am fairly comfortable with that.

    But the housekeepr, Mrs Robusto, is not

  20. #20
    Senior Member robusto's Avatar
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    Something inexplicable happened a few days ago. The grinder was overcome with nostalgia for its old ways.

    It loves those good old days when it dominated conversation in the kitchen for 20 seconds at a time.

    When it ground away at a deafening roar, everyone else shut up and listened. Cos we can't be heard over it.

    For 20 seconds it ranted and raved to produce 20-22 second of grinds.

    Now, because it takes just half the time to do what ig used to do...the Cunill missed its pre-eminent place.

    So, it began with baby steps. First, 11 seconds for 22 grams. Then 12. Now I swear, it's slowed down to almost 15 seconds to grind the same amount.

    Surely the burrs can't degenerate THAT much from brand from brand new in a matter of weeks?

    ....Justvwhen you think you're finally on top of your game...something comes along to keep you on your toes. Again.

  21. #21
    Senior Member Yelta's Avatar
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    Quote Originally Posted by robusto View Post
    Surely the burrs can't degenerate THAT much from brand from brand new in a matter of weeks?
    They certainly can if they happen to be aftermarket burrs.
    Bought a set of non genuine burrs for the Rocky once, big mistake, got a couple of months out of them and they were stuffed, ordered a set of genuine Rancilio burrs, they lasted another 3 years until I sold the grinder and were still going strong.

  22. #22
    Senior Member robusto's Avatar
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    That thought did occur. They came from one of our sponsors here.

  23. #23
    Senior Member Yelta's Avatar
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    Quote Originally Posted by robusto View Post
    That thought did occur. They came from one of our sponsors here.
    So did the dud set I got for the Rocky, you need to ask the supplier, are they genuine ****** burrs.
    From memory I finished up buying the real McCoy from Jet Black Espresso.

  24. #24
    Life-long Learner DesigningByCoffee's Avatar
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    Hi Robusto
    Don't know if this is a bit left field.
    I used to have an FJ40 landcruiser. The wipers used to go like the clappers when you switched them on - then somewhat inexplicably slowed down until they were virtually useless! It was lots of fun in the rain!
    Could it be the motor - not the burrs? Sounds like an unpleasant (and unwelcome probably!) suggestion - but might explain the gradual slowing?
    Justa thought
    Matt

  25. #25
    Senior Member robusto's Avatar
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    Reminds me of those old vacuum-operated wipers. I just don't know.

    Yelta, not sure what are genuine burrs, as many are made by some manacturers who supply different brands, and they are interchangeable.

    As long as they are well made from hardened steel should not be an issue.

  26. #26
    Senior Member Yelta's Avatar
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    Quote Originally Posted by robusto View Post
    Reminds me of those old vacuum-operated wipers. I just don't know.

    Yelta, not sure what are genuine burrs, as many are made by some manacturers who supply different brands, and they are interchangeable.

    As long as they are well made from hardened steel should not be an issue.
    Certainly not so with Rancilio burrs, genuine are stamped Rancilio with the logo, Mazzer come in a Mazzer branded bubble pack.
    Trust me some aftermarket burrs are very inferior, I'm sure others will agree.

  27. #27
    Senior Member robusto's Avatar
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    Time flies. I see it's been a year since my last posts about the Cunill grinder.

    An update...which essentially means that after a year of bliss--I'm back to square one.

    Everything was going fine, grinding for some 10 seconds for a 20 gram basket.

    Until we went away for a fortnight.

    When we returned, using two week old beans, and having not touched any settings, I pulled a gusher. About 10 seconds for a double shot of 20 grams.

    Hmmm. Must be my beans have really gone stale and dehydrated, thinks me.

    So adjusted the grind to compensate-- one notch from touchey-feely. Pretty much the same result. Gushers.

    Roasted a new batch...and another over the last 10 days since this calamity manifested itself on our return from holidays....but still gushers from the Grimac's portafilter.

    And that's despite the finest setting available.

    I've taken the grinder apart and reassembled it thrice...but still the same result.

    Cannot believe how a two-week spell can change things so radically.

  28. #28
    Senior Member robusto's Avatar
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    Being the never-say-die, obstinate man I am I refused to give in.

    I spend the entire day working on the sweeper plate upon which the lower burr sits. hammering it, filing it, sanding it, machine pressing it, trying to get it perfectly flat. (The plate itself precariously perches on a 3 mm round "ledge" machined into the motor armature).

    I lost count of the trial and error assembly of the lower burr. Scores of doing and undoing the nut which holds the burr onto its plate.

    I even dismantled the upper burr a few times. Seems I have done all I can do, and have sacrificed almost a kilo of good beans. But best I can get is a 16-second extraction. And that's with the burrs just about rubbing each other.

    The grind is gritty....And yet I recall when such a fine setting would produce wheat flour-like consistency. And I recall the good old days when that finest setting would choke the Grimac.

  29. #29
    Mal Dimal's Avatar
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    G'day Robusto...

    I'm not at all familiar with the Cunill mate, sorry; but Attilio of Cosmorex has helped a few CSers with Cunills over the years so maybe it's worth dropping him a line. He may have a couple of helpful suggestions...

    Mal.

  30. #30
    Senior Member robusto's Avatar
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    Thanks Mal
    Attilio previously replied that I should contact the importer, but I don't know who that is.

    However......there may be good news.

    More tinkering a couple of hours back, and this produced a promising result. The first such one.
    But the beans were roasted just yesterday, and ground on the very finest setting, so not conclusive yet.

    Stay tuned.
    Dimal likes this.

  31. #31
    TOK
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    Quote Originally Posted by robusto View Post
    Thanks Mal
    Attilio previously replied that I should contact the importer...


    enquiries@ronita.com.au and
    Phone: 02 87837878

    Liverpool in Sydney.



  32. #32
    Senior Member robusto's Avatar
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    Thanks,Tok. Much obliged.

    An update...

    Last night I removed the four small bolts which attach the motor to the grind chamber. I pulled the motor free, and offered it back to the underneath side of the chamber to re-insert the bolts. Obviously, the motor, and hence its shaft, has to be perfectly perpendicular to the chamber. Maybe before it was slightly off centre because of the alternate hot and cool days we've had this summer?? Dunno.

    Having re-assembled everything again, And using a piece of paper as a feeler gauge, I noticed this time the paper could not be easily pulled from between the lower burr and my "dial gauge". Very promising.

    This morning, withy unrested--barely 2 days--beans, extraction took 41 whopping seconds. Joy oh joy

    One notch back from touching burs, and it was 35 seconds. Ah, at last, some leeway.

    Of course, the coffee was undrinkable without a teaspoon of sugar as the beans need another couple of days de-gassing.

    See how we go from here.

  33. #33
    Mal Dimal's Avatar
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    Excellent news mate...

    Sounds like you're back in business, whatever the original 'fault' may have been...

    Mal.



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