Mazzer Super Jolly bearing removal tricks: My grinder rebuild

Grinders are one of the keys to exceptional espresso. Discuss them here.
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delicious_espresso

#1: Post by delicious_espresso » Feb 25, 2018, 9:52 pm

I recently got a great deal on my first real grinder, a Mazzer Super Jolly. I've owned a couple Pavoni Europiccolas and am very happy and proud to finally own an all-metal commercial burr grinder. I've been using a laughable pushbutton blade grinder and flour sifter so far, and miss my cafe job but love my lattes. So it was just a matter of time until I got the right grinder. On my budget, this means a commercial grade, super-affordable fixer-upper.
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I got it filthy and beat up for $100 shipped. Ad said very rough condition AND parts only, but knowing how ruggedly built these are, I bought it undaunted. I beat it back into shape, bathed it in acetone to get all the old tape residue off, made a blood sacrifice to the coffee gods. While impact driving a bolt back into the doser with my finger pressed against the metal dosing spout shield, I got a cut almost deep enough to require stitches. Four days in a bandage and it's closed up just fine. This one's a keeper, it has it's own scar on me already! The motor ran with no unusual noises, so I ordered some burrs. When they arrived, I installed them, but now after cleaning, I noticed the upper bearing had seized... or something. I figured all the cleaning solution I used while blindly swabbing under the lower burr carrier with q-tip after q-tip must have seeped into that upper bearing. The motor strained, I would turned it off, tried turning it manually, but it only had a few degrees of rotation. Seemed like a seized bearing. I know it's a brushless motor, and I'd had it apart enough to know nothing was jammed in between the stator and rotor.

I went to take it apart and did a few searches on how people got theirs apart. The first hurdle was the lower burr carrier. I could get the bolt off with my Ryobi impact drill, socket adapter, and 13mm socket easily. While the bearings still spun, I tried getting it off for cleaning purposes, but gave up because, hey, the motor still spun.
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I had read that one guy had taken the bolt off and pried up through the grinding chamber-to-doser chute with a screwdriver. You could pad the screwdriver with leather or wood or some material to avoid marring the burr carrier, or be careful what part you lift on. I knew my motor shaft was a little too gummy and rusty for prying action alone. I also know how to heat aluminum pressed to steel with a blowtorch to get it to expand enough to come off easily. So I heated it up really quick. There is an o-ring under the lower carrier, but nothing else that can melt. A heat gun would also work. Once heated, only minimal prying was needed to lift it up. Some prefer to run extra-long bolts through the three holes until they hit the surface below and lift it up, but that usually scars the bearing shield plate. Only a couple bucks for a new one, but heat and gently prying through the chute works with no damage. You're really just lifting it out because the aluminum expands a lot. This is really apparent with the lower bearing removal.

With that part out, you can now remove the bearing shield plate with 3 screws and see the bearing.
(I used a photo from the future, imagine a crusty, seized-up bearing:)
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Now we go to the bottom and label and unplug all the wiring including the motor start capacitor and ground wire from the motor's bottom bearing flange plate. Then we remove the four screws holding the bottom bearing flange plate to the body.
Up above, with the lower burr carrier removed, and the lower flange's screws removed, the motor's rotor is hanging by the upper bearing. It can now be safely tapped down and out with a block of wood and hammer, or bearing press. It should not take much force.
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With the rotor out, a long socket extension (10") coupled to a socket with an outer diameter of 3/4" (I used a 9/16" deep) or pipe of similar dimensions can be used to tap the upper bearing out of it's socket with the machine body inverted. Drive it out from the bottom on the inner race to pop it out of the recess. Don't be shy! Be bash-ful.
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There is a black plug in the center of the lower bearing flange. Once removed, there are threads matching that of the bolt holding the upper burr carrier. That bolt is not long enough to push the motor shaft out completely, but the next longest one at the hardware store bin with 8mm (m8x1.25 thread pitch) will. I used the Ryobi impact driver drill again, just holding it. You can also put the flange in a vise and use a rachet or breaker bar or wrench to turn the bolt.
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With the rotor shaft pushed out of the bearing flange, I put it upside down on blocks and heated the aluminum with a torch until the bearing literally fell out by gravity. A heat gun or a bachelor's oven at 350 should also work.
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Some espresso machine parts places want up to $35 per bearing. There is one out there who only want $12 ea., but McMaster-Carr has them for $10-$12. As long as you get one with the number 6202- in the part number, you can't go wrong. Some are abec-1 others are abec-3, and some are metal shielded, some are sealed. Sealed is more, well, sealed from things like what caused mine to seize, and are preferred over the shielded, but as long as they are not "open" type, they will work well for a long time. I have a better idea of what I'm getting for the price from McM-C, so I went with the ABEC-3 (higher precision rating) sealed ones for $12 each, and they will be here on Thursday, when I will finish this write-up with more photos than the teardown.

dilin

#2: Post by dilin » Feb 25, 2018, 10:17 pm

Keep us posted, that's some cool info.

I have a SJ with a '64 EP and I'm loving it.

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delicious_espresso

#3: Post by delicious_espresso » Feb 27, 2018, 5:11 am

I couldn't wait until Thursday for the bearings so I called a local bearing distributor who is only a bikeride away. Why didn't I do that in the first place? the bearings were even more affordable. Then I went to the hardware store for a replacement tension pin.
It was kind of fun getting the old one out.
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I cleaned up the lower burr carrier. I see why the roll pin was smashed, there were nicks along the edges of the three fins, probably not visible in this photo, but it would be from the side view.
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Now I can drive in the upper bearing. Helps to heat the aluminum, but will drive in without heat.
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Then drive on the lower bearing.
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That's as far as it goes.
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Then I heat the crap out of the bottom flange and basically drop it on to the lower bearing. It actually requires a couple taps, but it's really all the way on, no doubt when I heat it to expand the aluminum. Then I thread the wiring through the hole in the flange as before, and pound the center of the flange until it seats, and bolt it to the body. Then I put all the wiring in place like before.
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Back to the top, I reinstall the shield plate and o-ring, and prepare to align the roll pin with the slot, tap it into place, and drive the final bolt for the upper burr carrier. I made sure the bearing was still seated in the case, some report it moving up and out of the body when the rotor's steel shaft is driven in since the aluminum is not as strong of a press fit. I lucked out and it was still seated.
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Generally, by the book, it would be best to install the bottom bearing and flange with the upper bearing out, then heat the aluminum body so it expands enough to relieve most of the press fit, and drive the upper bearing using force only on the inner race while pressing it onto the rotor's shaft. I had to remove the upper bearing from the shaft after accidentally driving it on to the rotor first, and I have to say, I believe it didn't cause any damage to the balls or races from the feel of it. I've done that with wheel bearings too.

Put the burrs in, upper carrier, adjuster...
Still dialing in the baseline for the grind.
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delicious_espresso

#4: Post by delicious_espresso » Feb 27, 2018, 5:48 pm

Also, I did machine off the bent section of the upper burr carrier. It will still take a hopper, I only removed the area with damage and a set screw. No cafe ever worked in used the set screw anyway, so machining off the upper half inch was no big deal. While I was bidding on the grinder, I was forming elaborate processes I would use to repair it in my mind. The simplest solution was the best.
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I also found it surprisingly easy to beat the dented doser back into shape, and can hardly tell it was so smashed up anymore.
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I could not get the clear plastic par out, however. I did also attempt to remove the bottom floor of the doser that is riveted to the body, but I mainly wanted to clean it and put it back together, and as much as I would love to get the old coffee out from between the glass and the doser, I also didn't want to break anything and have to order more parts at the moment. I like to have two of everything before taking on full doser-off restorations. That's why I left the finish alone. I knew that once I got the parts to be able to use it, I wouldn't want to go back to my old system of grinding while I waited. So the next $100 shipped grinder that comes along will be the first to receive a semi-gloss bare aluminum medium polish and nice parts.
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walt_in_hawaii

#5: Post by walt_in_hawaii » Feb 27, 2018, 8:24 pm

Hmm, I just received my used SJ yesterday off fleabay and will be posting some initial evaluation pics on the "frankenjolly" thread soon. I plan on dumping my doser and converting to single serve... if you need parts from it or the entire doser even, holler at me and you can have them for whatever shipping costs to get it to you. I'm in Hawaii, 96707. Have the lid for it too.

Oh, by the way, I might do the same thing you did for bearing replacement even though I don't feel any play in mine, just because and its one less thing to worry about when chasing fine consistent grinds... if you could post both bearing part numbers from McMaster-carr, I'd appreciate it! have to order the same set for mine... same bearings for top and bottom? i'd prefer smallest possible amount of play (tightest tolerance), please.

aloha,
walt

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delicious_espresso

#6: Post by delicious_espresso » Feb 27, 2018, 11:48 pm

Hi Walt,
Yeah, the vanes in my doser have a couple big bad grooves on the bottom keeping them from sweeping. I'd take the doser from ya to fix mine. Also looking for a small hopper. Have you heard of using the "octopus balls" funnel to make your own doserless funnel? If you're Frankensteining things, I would think you'd be handy enough to save a couple hundred and polish the inside and drill some holes yourself. Or get one from fleabay predrilled and cut for $79 and polish the inside yourself, even comes with a gasket.

walt_in_hawaii

#7: Post by walt_in_hawaii » Feb 28, 2018, 3:31 pm

The sweep vanes (3 of them) seem to have hit some stuff in the past; they have little dings, especially the vane at 11 o'clock position. Is the floor that the vanes sweep also scarred? If I were you and haven't yet assembled it, I'd put a piece of fine sandpaper on a piece of glass and smooth out the scars on the vanes before reassembly. If you have access to a lathe, you might want to put the floor portion (the swept part) into the lathe and recut the floor so its smooth again. This will all be dependent on whether or not the vane height can be adjusted, of course. If the vane height is set and cannot be moved, then you cannot cut the floor unless you plan on installing some sort of sacrificial sweepers like plastic or rubber arms onto the vanes. Thanks for the pics! great shots.... I plan on disassembling my Super Jolly this weekend.

aloha,
walt

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delicious_espresso

#8: Post by delicious_espresso » Feb 28, 2018, 4:11 pm

Just the vanes are galled up. Seems like coffee resin buildup actually might have worn them away, or at least that's what was caked heavily on the floor when I got it in those notches. Pretty deeply scarred, worse than what you're describing. The floor is flat. The two downward screws are oval head, and I thought that was what caused it, but when tight, they are recessed enough to be out of the way. Perhaps at some point in the past they were loose enough to be contacting the vanes. I suppose I could create a plastic sweeper add-on.

I can't tell if the bottom is spring pressured against the floor, the vanes are a 2-piece system that are sort of telescoping, I forget if the depth changes only upward or if it pushes to the bottom too. Anyone know?

walt_in_hawaii

#9: Post by walt_in_hawaii » Feb 28, 2018, 4:26 pm

I doubt the vanes actually are supposed to touch the floor. Probably they 'fly' just above them and utilize the air curtain to push the grounds through; that's what's causing the spurt of air when the grinder runs out of beans and is pushing only air at the end of the grind. Also, coffee beans occasionally have small rocks in them (sometimes) or other impurities... I've caught my fair share in the greens I roast. Some places more than others; I seem to find more bug-riddled beans and small detritus in south americans than Africans. since they affect the taste, I remove them prior to roasting and toss them... probably something approaching 10%? get tossed. But in commercial beans, it would probably be every man for himself, so luck of the draw if your vanes find a stone or something in there.... ouch.