Hey folks,
I rebuilt a Cremina this weekend, but have run into a bit of a pickle with the group.
the lower nut on the piston shaft is torqued down as far as it will go, yet it's not stopping the piston. Rather, the fork from the lever is hitting the top of the group (the "bell" if you will). The shaft is screwed into the piston as far as possible and all the parts are from the same Cremina. I didn't think to check before the tear down, but given the complete lack of wear on the group, it doesn't look like this happened prior to the rebuild.
Below are a couple of photos that should help explain my predicament.




Thanks for any tips/advice.

Wow, guess rebuilding Creminas was the order of the weekend! Mine, that I wrapped up this weekend, is below.

What I learned is the brew-group is composed of some pretty soft brass*, and it's not uncommon for the back hole, where a lever pin and roller pin/sleeve goes through, to become deformed. This creates some slop in there, which I believe could allow the lever to hang lower than intended, and to come in contact with the business-part of the brew group. The lever on mine barely sits above the brew-head. I may make a trip to either a hardware store (though I'm not confident they'd have what I want) or to a machine-shop to see if I can get a larger outer diameter sleeve made that will eliminate some slop.

*I know it's soft because the plating company I used accidentally dinged the front of the brew-group, but was able to remove the ding by rounding out the edge where the ding was - you can see this rounded detail in the picture below if you compare it to a standard Cremina brew-group. I was bummed that they dinged it, and it was a bit of a hassle to get it corrected, but I'm very happy with how it turned out.

Bob,
Great work on the Cremina - judging by the handles, it looks to be an older model.
How did you get the faceplate so mirrored? It looks incredible.
I checked the rear slot - that was my first thought too, but it's in excellent shape, no warp/bends whatsoever.
I'm completely flummoxed by this. On the bright side, the machine works well and in theory I could simply use it as is, but I'm sure folks on HB can relate to my frustration at having come so far on a successful rebuild only to be derailed by a few millimeters of extra piston shaft...

Thanks Garth. This was a machine that Jim Piccinich was selling back in February, and I've figured out it's a bit of a Frankenspresso machine with parts off several different Cremina vintages. The handles will be gone as soon as I get replacements from OE.

As far as the finish of the chrome and stainless pieces, I had all that done by Orange County Plating. They electro-polished the stainless, and brought it all to near-new mirror-like condition. To see where the machine had come from, it's hard to believe it's the same machine.

Bummer, and great, to hear you don't have any deformation in that back slot. I watched an OE YouTube video over the weekend to make sure I was putting the piston assembly back together properly, and in the video, Doug comments on the deformation - guess it's somewhat common with Cremina machines. As you mentioned, if that looks fine, just wait until the real Cremina experts chime in. I hope it's a simple fix for you.

Similar situation on my La Pavoni. I ended up installing bronze bushings in the slot to correct the slop:

Bronze bushings for worn La Pavoni lever - DIY

Not sure if that's what is causing the bottoming out or not on your machine however; it doesn't really look like it.

I'm not really familiar with your machine, so just a shot in the dark: are you sure the lever isn't on upside down? Perhaps the holes are not exactly in the center on the lever?

Ray

Hi Ray,
As a Eurobar and Europiccola owner that was my first thought too! (re: the fork being upside down), but it appears to me that the holes are dead center on the Cremina forks.
I've gotta give some points to Pavoni on this one, the offset fork holes would seem to give the lever more clearance...

Did you remove the rod from the piston? Maybe it's upside down?

What stops the travel in the group head?

Ray

There is one other solution to your predicament... The threaded nut that fits on the top of the shaft, under the acorn nut, is made in varying thicknesses and can be bought in stainless steel. Buy a nut that is roughly double the thickness of the current nut and mill it out so the first few theads in it form a cup that will fit over the shaft. That way you will get the additional eighth of an inch or so to make a new stop for the travel of the shaft.
From McMaster Carr:
Metric Flange Hex Nuts
Size ------ height mm---- Stock Number
M10 17---- 17mm------- 91005A037


Metric Heavy Hex Nuts
Size------ height mm---- Stock Number
M10 17------ 10mm ------- 90725A720

Both of these nuts are in zinc plated steel... but that was just a fast search.

Another thought is that the nut thta Olympia used may be a thin nut. The standard nut sold in stainless is 8mm - 8.4mm thick... So you can measure the nut you have to see if it is a thin nut. Perhaps a standard nut would do the trick.

Another option would be to use the current nut that you have and get an additional nut in stainless at 8mm thickness and bore the current nut deep enough to use it as a collar by leaving a thin lip to set on the top of the shaft. Then use the new stainless nut to be the one that sets the depth. In other words the old nut would be a washer that would take up the distance of travel by allowing the shaft to be drawn up into it to the lip while the top nut draws it up and takes up the play that you currently have.

Im no expert but could have the rod backed out of the piston a little bit? You may be able to just pull the pin and see if the rod will run in any more

I agree with the other suggestions, another concerning the modified nut, is it possible the factory jam nut is relieved as suggested and you installed it the wrong way?

I spent last night soaking the group of another machine I'm restoring (one that came without a piston) so hopefully tonight I'll have the time to take out the piston, check that it's screwed in tight to the rod and see if I run into the same issue using a different group.
I'll be sure to post an update. In the interim, if anyone else has the same issue or other thoughts on how to fix it, I welcome all suggestions.
Thanks,
GB.