Announcement

Collapse
No announcement yet.

Cunill Grinder misaligned burrs

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Cunill Grinder misaligned burrs

    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
    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 Files

    Comment


    • #3
      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...

      Comment


      • #4
        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.

        Comment


        • #5
          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

          Comment


          • #6
            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

            Comment


            • #7
              Have you considered the possibility that you may have bent the shaft when undoing the nut holding the bottom burr?

              Comment


              • #8
                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.

                Comment


                • #9
                  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.

                  Comment


                  • #10
                    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.

                    Comment


                    • #11
                      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 Files

                      Comment


                      • #12
                        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--lol--a much coarser grind is called for.

                        Comment


                        • #13
                          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.

                          Comment


                          • #14
                            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.
                            Lol 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.

                            Comment


                            • #15
                              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.

                              Comment

                              Working...
                              X