Thanks for the hints on where to find a 30 mm socket. Fortunately, with a bit of understanding on how the boiler was put together (it is a ~20 mm stainless steel draw bolt through the middle), some penetrating oil, a 300 mm adjustable wrench and a two-pound rubber mallet, the nut moved pretty easily. Definitely do this with the boilers (both) still in the frame.

Apparently the draw-bolt construction was only on relatively early models, later replaced with a bolt-on cap, like the steam boilers (are supposed to have). The welded-on cap on my steam boiler, I was told, was a not-uncommon way to repair the boiler when the crown inside the boiler that was threaded to receive the end-cap bolts became stripped. It's made descaling a pain, as I have to dissolve the "bladder stones" down small enough to fit through the ~3/4" tapped hole. I've been using ~2% w/v citric acid in water (~1 Tbsp./qt.) and finally have most of it out. Some rather amusing bits have also come out



The cartridge element for the steam boiler (likely non-stock) is a Watlow Firerod stamped 240 V 2300 W 0042 J14A39-BG 12 From the resistance, it it probably in good shape.

The brew boiler element, once the scale came off, reads "RICA '04 '89 220V 1300W" which suggests that it was replaced sometime in the early 90s. Rica is still around, so they may be able to help. I found a couple La Marzocco part numbers:

• LR340/220 W1300 220V cm.21 1/4" 1gr
• LR341/220 W1600 220V cm.29 1/4" 2gr

Neither seems to be an "exact" match as the element in hand extends about 42 cm (~16 1/2") into the boiler.

Threads are always amusing. The auto-fill is American compression fittings, while the rest of the plumbing has metric-sized nuts. The leg sockets (one of which I need to replace) will take about ten turns of a 3/8"-16 bolt; they're really M10x1.5. The whole BSPP vs. NPT comp/flare thread near-but-non-compatibility is always an experience.

Anyone have a suggestion for cleaning the valve bodies and stems? The ultrasonic with a bit of dish detergent hasn't been cutting it. Normally I'd go for carb cleaner, but between it probably being on the list of banned-in-California substances and not something I'd really want in my coffee water, I was looking for something a little less harsh.

The GS is moving ahead, though slowly. A new leg on the lower frame means that the frame is ready for the powder coat shop tomorrow.

On closer examination, this machine definitely has been "worked over" once before. What I thought was corrosion on a frame member turned out to be likely what was the pitted surface left after some pretty heavy rust had been removed and the frame had been repainted. From what I can tell, this machine was originally "the usual" colors; red-orange side trim panels and upper frame, dark grey-brown end panels, and black for the remainder of the frame. I'll be returning the upper frame to as close to its original color that I can using RAL 2002 and a black hammertone (original, I'm told) on the rest.

The groups have been a challenge to get apart. The valving, I was told, "comes off easily," which certainly wasn't the case for me. I ended up using a torch to heat it several times until things loosened up and I could get a putty knife in to gently ooze the brass top plate up and away from the chromed body. From what I could tell, there was a thin paper gasket between the two, as well as an o-ring. While some of the drawings I've seen for these groups have a gicleur/giggler on a tube part way down the throat towards the brew boiler, these only have a hole in the lower cover of the valve assembly.



I still need to get the dispersion block and cone out. I've been soaking in penetrating oil for a while now, both from the top (inside the group casting) and from the bottom (screen side).

In trying to fabricate a tool to do it, I was very puzzled as it seemed every time I went to check the thread that holds the screen in place, it was a different size. Well, that is because some repairman of the past crammed a 10-32 screw into the M4 tapped hole. Bah. I'm hoping that Helicoil or the like will be able to repair that when the time comes. I haven't had much luck with trying to get a M4 screw to get any "bite" into the dispersion code dimple. The cone dimples are about 14 mm from center to center and apparently a little under 4 mm in diameter; the dispersion block holes are about 49 mm center to center and a little over 4 mm in diameter.

In looking at the general group casting and operation, its not much different than that in Cutaway of La Marzocco saturated grouphead

WARNING -- SPOILER AHEAD

I have to say that once I pulled apart the paddle-group valves, I was disappointed as I was expecting something more sophisticated. There basically is a ~2mm hole in a piece of Teflon and a rotor with a matching hole for the inlet and exhaust valves. No fancy progressively opening valve or anything. Hey, but it feels good somehow to slide the paddle over, right? It may function differently under pressure, but here is how it works:

Top of the group (brass, top left) has a small hole in the central area that leads to the exhaust tube. The white Teflon disk has two holes locating pins and a matching hole for exhaust.

The bottom of the valve assembly (dark brass, bottom center) has a hole that leads to the grouphead interior (either line or pump pressure) as well as a similar Teflon disk with locating pins and a matching hole.

There is a rotor between the top and bottom Teflon disks that is drilled through (~2 mm) so as to align with one or the other exhaust/inlet hole, depending on the angle of rotation. From that through-drilled hole, there is a galley drilled to the relief around the shaft that runs through the assembly.

The shaft takes the paddle on top to turn the rotor and has ports in its side that allow water from within the valve to flow back and forth to the dispersion block. There are seals above the ports, to the bottom of the valve assembly, and (effectively) to the dispersion block beneath.

I'm still somewhat puzzled as to how there is any flow when the paddle/rotor is in the "middle" range. Perhaps it will all become clear when I reassemble one of these with parts that have their elasticity intact.









The shaft can be "tapped" out of the rotor gently from the top

Metric Sheet Metal Screws

Thankfully metric machine screw availability in the US is significantly better than it once was, but what about sheet metal screws? Having the "pleasure" of dealing with a 10-32 screw in a M4 hole, I didn't want to mess up the already tenuous grip of sheet metal screws by cramming an imperial one in.

The good news is that, from what I can tell, the metric ST threads are "a soft conversion from imperial" so that good quality sheet metal screws from a local US supplier should be able to be used interchangeably. Of course, try finger-threading one in before you believe that you have the right size!

The metric designation is ST for "self tapping" followed by the body diameter, in mm (with a comma as the decimal separator). The ISO number corresponds with the US "gauge" size of a screw.

Lengths are generally in a close mm equivalent to 1/8" increments. The head sizes should be effectively interchangeable as well.

This is only for self tapping "sheet metal" screws, as in the photo below

• ST 2,2 -- ISO 2
• ST 2,9 -- ISO 4
• ST 3,5 -- ISO 6
• ST 4,2 -- ISO 8
• ST 4,8 -- ISO 10
• ST 5,5 -- ISO 12

The bad news is that the pitch may not be the same

Depending on the screw, it can be too close to call (the small screw), a little off, or completely off. Please, please compare the pitch first, then finger-thread it in if you think it is close enough. There are two common pitches in use; the hardware store provided only the coarse (A) threads. The two that don't match in the photo are the fine (AB and B) threads:

Coarse: (#2-?, #4-?) #6-18, #8-15, #10-12, #12-11
Fine: #2-32, #4-24, #6-20, #8-18, #10-16, #12-14

Here is some detailed information on sheet metal screws (imperial) from SC Fastening Systems.

If you don't have a pitch gauge, Metric 60-Degree Whitworth 55-Degree Screw Pitch Gauge Tool (from Amazon) surprised me with its completeness (metric and imperial), quality (made in Germany and has screw-post tension adjustment for the blades), and low cost (under $10). (I can't visually tell any difference between my 60-degree imperial gauge and the "55-degree" blades of that unit.)



Looks like I'm still searching for replacements for those long, rusty screws that hold on the side panels.

Most of the suppliers I used in the past for metric hardware have closed here in the San Francisco area (Olender's, Industrial Hardware). Ace hardware stores often have the Hillman line of fasteners, which seem to be somewhat better quality than the Crown products sold at stores like Home Depot, Lowes, and OSH. Whenever you can, getting graded parts (8.8, 10.9, for example) helps get you out of the "cheapie" quality.

I have found a shop that caters to the motorcycle market that does have a great supply of metric fasteners locally:

Global Metrics
519 Marine View Ave # K
Belmont, CA 94002-2568
(650) 592-2722

They do not have BSPP fittings, unfortunately.

Maryland Metrics has a lot of information on metric fittings, and seems to have reasonable prices on box lots (typically 100 pcs). I have not ordered from them yet.

Reyher (Germany) has a nice catalog with fastener dimensions that is useful for reference.

Boellhoff (Germany) provides another great reference on metric fasteners.

Update -- Here is a table that includes what I've been able to pull together so far.
#7 isn't a "preferred size" in metric, but you might run across them



Information mainly from pages linked off http://www.lubkerdist.com/specifications.htm

Jeff,
I have some exploded diagrams of the group if you need them to put it all together. Also it shows part numbers for O-Rings and Rebuild kits etc. There is a special socket made for the shower screw insert and the diffuser block but looks like you got them already.


BillC

Billc wrote:Jeff,
I have some exploded diagrams of the group if you need them to put it all together. Also it shows part numbers for O-Rings and Rebuild kits etc. There is a special socket made for the shower screw insert and the diffuser block but looks like you got them already.


BillC

I'm getting ready to rebuild my GS and would love it if I could get that info from you, Bill. I rebuilt it about 18years ago and was never sure I did as good a job as if I'd had a diagram and some reference points.
Bernie

Jeff-Thanks so much for putting up all this info. I'm running a GS I bought about 25 years ago and it's time for another gasket job. Your work has been really great as I've never seen much on these old workhorses. Thanks again.
Bernie

Hi Jeff

If you need any metric thread bolts and or nuts, just let me know which ones and I'll get them for you.
They are standard 'off the shelf' stuff here in Aus.

Good progress you've made.
Keep it up.

Thought I'd put up a photo of my machine, GS 2grp Paddle also, so far anyway

One of Portland's true treasures is General Threaded Products, a shop that does all manner of nuts, bolts and screws - and nothing else. They've had items there that I'd dispaired of ever locating, and I think they even tapped/died me some otherwise unavailable items on the fly. (I suspect sometimes that the whole coffee culture up here would never have developed without them to provide obscure hardware for even more obscure Italian machinery.)

I don't think they have a web site, but their phone number is 503-234-5248. I've always just walked in, so I'm not sure what their appetite is for "remote" orders. Regardless, if you need a pair of feet to go pick something up, match an existing piece or mail an item to you, just PM me and I'll be happy to run over there and get it out to you.