Making brass cap for la Pavoni Europiccola, etc. - Page 2

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TomC
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#11: Post by TomC »

Do you have different bolts securing the lever? It looks like the nice finished cap nuts that are on top of the piston.
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KurtAugust
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#12: Post by KurtAugust »

RayJohns wrote:If you produced some caps with nicely machined in thermometers, you can be sure TomC (and probably others) would take a serious interest in purchasing one :)
Hell yeah! As much as I love my temp strips, they become brittle and hard to read after a while. That and the whole pid afterthought of course...
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rpavlis (original poster)
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#13: Post by rpavlis (original poster) »

I became annoyed with the clips holding on the lever. I discovered that the moduli for brass would certainly be high enough to replace the metal rods holding the lever with brass--and brass is much "slipperier" than steel. I took a piece of brass stock and turned it down to the correct diameter, and then threaded the ends and put acorn nuts on the end. Now I can have the group off and disassembled in two or three minutes! One could use steel for this too, but I used brass since I had some and I thought it is sort of self lubricating. I made it fit a bit tighter than before, so it has less "play" which I like.

I made more Europiccola brass tops. There is a learning curve. I put one I made on my 1980s type Europiccola too. I have ordered a pressure gauge, since I could not find any locally. The plan is to make a cap similar to the ones I made before, but to drill and tap a hole through the centre to attach the gauge, and another part way into the cap for a simple thermometer well to accept a thermocouple.

Another thought is to make a wood top and drill a hole clear through the wood top and into the brass for a thermocouple well. One could also make a well for a simple glass thermometer.

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TomC
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#14: Post by TomC »

It looks much nicer, with a finished detail like you have it now. With the added bonus of not losing those tiny stock c- clips either.
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rpavlis (original poster)
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#15: Post by rpavlis (original poster) »

Some day very soon I am going to replace the pins on my other machine the same way.

There are three ways to get temperatures through the cap. One is to have a thermometer well and insert an ordinary laboratory thermometer--cost about $6. The second is to have a thermometer well and insert a thermocouple thermometer probe. The third is to find some way to attach some kind of thermometer so it is present all the time.

The proper way to do any of them is to obtain a piece of machinable copper--it is a dramatically better heat and electrical conductor than brass. It would need to be about 12mm in diameter and perhaps 25 mm long. One could thread it on one end and drill a hole from the threaded end nearly to the far end. A hole could be drilled and tapped from the bottom of one of my 32mm threaded caps, and this threaded into it. There would only be the thin conducting copper walls between the copper and the inside of the boiler. This should allow the thermometer to read very exactly.

If one were to do this, one could have a short wooden cap above the brass to enable removing the cap without burning fingers, and the wood would have a hole all the way through into the hollowed out copper tube on the other side.

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SAS
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#16: Post by SAS »

A big THANKS to Robert for machining me a brass filler cap for my La Pavoni.
I used walnut to cap the cap.
Here is the result.


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TomC
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#17: Post by TomC »

That is absolutely gorgeous! I can't wait to finish modding my EPC, it's going to be beautiful!
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rpavlis (original poster)
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#18: Post by rpavlis (original poster) »

Before I made the first brass cap I did not realise how difficult it would be to make the first one. It took a lot of thought and planning. When I discovered I could obtain M32x2 dies for half what La Pavoni charges for their lousy plastic cap, I bought the die and went to work. I spent a whole afternoon making the first one. It was an example of a project with a VERY steep learning curve. The technique that I developed is outline in earlier posts in this thread.

I originally put the tall wooden handle on the cap for appearance. However, I discovered, for me at least, it is much easier to put this cap on than the originals because you automatically hold it vertically when you put it in place and thus automatically get the threads aligned.

Cutting threads that large is a bit tricky, and when using a die it takes substantial torque. It is really important that the brass piece that is to receive the threads be turned down to fair precision. Best seems between 31.5 and 31.7mm. Much smaller than 31.5 would result in having to start over.

After learning how to do it, I can make the brass part of a cap in less than an hour!

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RayJohns
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#19: Post by RayJohns »

rpavlis wrote:Cutting threads that large is a bit tricky, and when using a die it takes substantial torque. It is really important that the brass piece that is to receive the threads be turned down to fair precision. Best seems between 31.5 and 31.7mm. Much smaller than 31.5 would result in having to start over.

After learning how to do it, I can make the brass part of a cap in less than an hour!
Suddenly a CNC lathe seems like something that would be handy to have around huh? :-)

Ray

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rpavlis (original poster)
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#20: Post by rpavlis (original poster) »

Some time ago I managed to find a suitable pressure gauge to attach to an espresso machine that had calibrations other than Mediaeval ones. I had planned to attach it to the sight glass, but it was too large to fit there. I decided that some day I would make a brass cap as described above and install this gauge on it. Today was that day!

I had just enough brass stock to make the cap. After having made several it took me only a few minutes to have it done, but without the gauge. The gauge had the bizarre pipe thread lack of a system of dimensions in which the diameter of the threads is totally unrelated to actual dimensions. The gauge I determined used the so called quarter inch pipe threads. Someone had me make something once that required pipe threads, so I had a set of small pipe taps and dies, 1/4, 3/8, and 1/2 inch, remember none of them are really that size. Since the tap was tapered, I found I had to drill the tap hole first with the stated drill and then with one slightly larger. After a lot of messing around I had neat flawless threads in the top of the brass. When I attempted to attach the gauge I discovered something, namely the gauge had 1/4 inch NON tapered threads! Fortunately I had the tapered DIE from the set. I screwed the gauge into the die, and it cut a lot of brass off the bottom of the threads and absolutely none at the top! Now the gauge had tapered threads too, and it fit the cap perfectly!

I gave the top of the cap a nice finish, finally ending up with sand paper, and attached the gauge. Just as I was attaching the O ring I noticed a problem. I had not drilled the hole all the way through the cap because I feared I might not be able to attach the gauge, and wanted to be able to salvage it as a normal cap if I were to fail! I removed the gauge and bored the rest of the way through the cap with a 5mm drill. I put it all together and it worked perfectly. Amazingly both the 1979 and 1999 La Pavoni have the gauge facing forward with the gauge screwed into the cap the same amount. Pressure, unlike temperature responds instantly on gauges. The pressure switch on the 1999 one turns off at 0.91 bar and on again at about 0.82.

After I tested it, I ground some coffee and had a cup of espresso! The time elapsed was at least an hour more than I anticipated because of the tapered vs flat thread issue, and because of the difficulty of using a strongly tapered tap.

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