How I aligned my Rancilio Rocky. - Page 2

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

#11: Post by BenKeith »

If you want to get it near perfect, make you an aluminum spacer that screws in, in place of the top burr and fits perfectly on the slot the lower burr fits in. Using a strong glue, glue and disc of about 400 grit wet/dry to the top piece. With the burr out of the bottom and the spacer in the top with the wet/dry glue to it, turn the motor on. Adjust the top down until it start rubbing the bottom burr holder. Using light pressure use the top to lap the bottom so it's a perfect match. I got my Rocky within 11 micron doing this and my Doge almost perfect doing this. The Doge was closer than I could reliably measure

coffinnate

#12: Post by coffinnate » replying to BenKeith »

I don't understand how this would correct an error in parallelism of the burrs. I can see how it could improve axial runout of the lower burr carrier. Am I missing something? How did you measure the 11 microns?

BenKeith

#13: Post by BenKeith »

Sorry, it's been so long since I've done mine, I forgot one step and I don't remember all I had to go through to do it. That was verifying the top burr was square in the holder. I did that in the lathe setting it up in a four jaw chuck with dial indicators but also had help doing it and it seems we also had to make piece or two to help hold them. It was one of those deals where you start doing it and figure out what's needed as you go. I do remember I didn't have to do anything to them, they checked good.

Knowing the top burr was sitting square in the head, The piece with the sand paper basically just lapped the bottom burr holder square with the top burr holder, but the top has to be square or it's just going to lap it square with the lowest point on the top burr.

If unsure, you can mount that spacer ring with the sand paper in one burr holder, let it lap the opposite burrs seating area, then knowing that one is flat and level, flip it over and mount it on the one you just lapped and let it lap the other one, Then both seating areas would be square with each other.

I have a lathe but my wife's first cousin who also happens to be a good friend makes precision aircraft parts for Boeing has several different mic's that measure in microns so I go to his shop when I want something closer than .001". He would not let his mother touch those mic's because the set he has is very expensive. He also has much more precision equipment that just the chucks on them cost more than my whole setup.

coffinnate

#14: Post by coffinnate » replying to BenKeith »

Nothing you did would have corrected the problem my Rocky had: a motor axis tilted relative to the grinding chamber and everything attached to the chamber. Even if you ground the carriers perfecty they would be perfect in only one position, any adjustment of the upper burr carrier would result in error.

What you did could have corrected axial runout. Did you measure runout or parallelism? Where did you measure the 11 microns you mentioned? I'm curious because measuring the parallelism of the burrs is pretty difficult, I needed to do it inferentially with several planes.

With the Rocky I have the motor shaft is nearly perfect, so the easy way to fix axial runout (given access to a lathe) would have been to turn the bottom carrier.

BenKeith

#15: Post by BenKeith »

I would have to go back and almost reinvent the wheel to remember how we did that one. I bought it in 2,000, used it a couple of years and was always having problem with extractions. So, about 2002, I basically did the same thing as you, I pulled it apart, cleaned it good and started measuring. Looking at the burrs through the exit shoot, you could adjust down with the motor running until you just heard them start to rub and you could see them touch in one area, turn it some and there would be a few thousandths gap. I took it over to my wife's cousins because he was much better setup that me. He got interest in it also, and the two of use spent most a day screwing with that thing. When done, he had the top head section and top burr was perfectly square. He was able to set up a precision mic somehow so he could measure the bottom burr holder as the motor was rotated and it looked perfect, and said the mic was showing about 11 microns, which could have been bearing movement of a number of other things. Anyway, when done, we painted the tops of both burrs with layout ink and just touching them, it rubbed it off both burrs.
I replaced the burrs in it about three years ago and checked the new one by painting the tops of them with black magic marker, gave it a quick spin with the two burrs touching and it still rubbed it off both burrs all the way around. Figure you can't ask for any better than that. When I changed the burrs in it, I converted it to doserless. I also bought a huge Doge grinder I converted to doserless, made a ton of mods to and checked, and worked on it until it was grinding about as prefect as one could expect. I does a much better than the Rocky. Makes a huge pile of very fluffy grinds with absolutely no clumps, while the Rocky makes more of a small clumpy grind, the Rocky still gives great shots and I still use it a lot. There is a light switch behind the grinder that the Doge makes very difficult to get to, but can get to it fine with the Rocky and that keeps the wife happy.

coffinnate

#16: Post by coffinnate »

BenKeith wrote:I would have to go back and almost reinvent the wheel to remember how we did that one. I bought it in 2,000, used it a couple of years and was always having problem with extractions. So, about 2002, I basically did the same thing as you, I pulled it apart, cleaned it good and started measuring. Looking at the burrs through the exit shoot, you could adjust down with the motor running until you just heard them start to rub and you could see them touch in one area, turn it some and there would be a few thousandths gap. I took it over to my wife's cousins because he was much better setup that me. He got interest in it also, and the two of use spent most a day screwing with that thing. When done, he had the top head section and top burr was perfectly square.
The upper surface of the top carrier wasn't finished in mine, since it only needs to be accurate enough to support the hopper in acceptable alignment. It is more important the the burr be in alignment with the axis of the threads. Ideally, all would be in alignment.
He was able to set up a precision mic somehow so he could measure the bottom burr holder as the motor was rotated and it looked perfect, and said the mic was showing about 11 microns, which could have been bearing movement of a number of other things.
Since this was measured as the motor was rotated, it was almost certainly run out. In my Rocky run out was very low, and could be made difficult for me to measure by rotating the burr relative to the carrier so their run outs canceled. The measurement you made would not address parallelism of the top burr and motor axes.
Anyway, when done, we painted the tops of both burrs with layout ink and just touching them, it rubbed it off both burrs.
This is a subjective measurement, made even more difficult by the slop in the threads.
I replaced the burrs in it about three years ago and checked the new one by painting the tops of them with black magic marker, gave it a quick spin with the two burrs touching and it still rubbed it off both burrs all the way around. Figure you can't ask for any better than that. When I changed the burrs in it, I converted it to doserless. I also bought a huge Doge grinder I converted to doserless, made a ton of mods to and checked, and worked on it until it was grinding about as prefect as one could expect. I does a much better than the Rocky. Makes a huge pile of very fluffy grinds with absolutely no clumps, while the Rocky makes more of a small clumpy grind, the Rocky still gives great shots and I still use it a lot. There is a light switch behind the grinder that the Doge makes very difficult to get to, but can get to it fine with the Rocky and that keeps the wife happy.
Because you never addressed the fundamental alignment of the motor shaft axis and the grinding chamber axis, your measurements may vary with grind adjustment. It is entirely possible that the Doge does better because it is in better fundamental alignment.

BenKeith

#17: Post by BenKeith »

What ever turns your crank. My primary concern is the matting surface of the two burrs. I could care less if it's machined so the motor shaft has a 10 degree tilt to it. If I can spin the motor or turn the top burr carrier, and the burrs maintain the same clearance all the way around and stay centered over each other, which according to some very good dial indicators and a couple people that know how to use them, it does, that's good enough for me.
As for the difference between to two grinds, that's because I removed the exit chute and enlarged the exit opening on the Doge so there is nothing catching the grinds to cause them to clump. Which is something that is not all recommended unless you have a way of dealing the huge amount of static the grinds will create, which I do.

coffinnate

#18: Post by coffinnate » replying to BenKeith »

Your posts are frustrating. After reading them again, carefully, I can't tell what your 11 micron measurement was of, or what machining steps were required to get there. Here's an example from your last post:

"If I can spin the motor or turn the top burr carrier, and the burrs maintain the same clearance all the way around and stay centered over each other, which according to some very good dial indicators and a couple people that know how to use them, it does, that's good enough for me."

If you're turning the top carrier, it moves up or down. Since your "clearance" doesn't change, you must be doing a radial measurement, but I have no idea of what.

I still have no idea how you measured burr parallelism at multiple top carrier positions.

It looks like a fair number of people are viewing this thread. Am I missing something?

BenKeith

#19: Post by BenKeith »

I should have never made the first post with it being a Rocky, because I forgot the work we did to get the top aligned on my Rocky, which made it not as simple as just making the spacers and lapping the two like we did after getting things aligned. I will just say, for that process to work, the top has to be properly aligned and is was very simple process for getting time almost perfect, after getting after getting the top right.
Now, as for all the details for having done it, like I said, that was close to 14 years ago and at 68 years old, half the time I don't remember what I did yesterday. On the Doge, I did three years ago, all I had to do was make the spacer and lap it a little, but it was very close to start with, and that was where my thought process was. You would expect a commercial grinder that cost close to $1,000 to have better machining than one that cost less than $300.

If it will make you feel better, I can go back and delete my post because for dang sure, I'm not going back and try recreating what the two of us did 14 years ago, just to satisfy a question on here.