La Pavoni + PID = better temperature control? - Page 16

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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RayJohns
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Joined: Sep 10, 2010, 5:31 pm

Postby RayJohns » Aug 10, 2011, 10:00 am

I finally made the adapter for the La Pavoni last night (and this morning) on the Taig lathe. I'm really happy with how it turned out. It's made from 360 brass. The threads are M12 x 1.00 and 1/8 NPT for the gauge. It was quite a bit more work than I thought, but it was a fun project nevertheless.

It's definitely nice to have the gauge back on the machine, that's for sure :)

Photos of turning the adapter are below:

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Getting ready to make the adapter. In the chuck is a 3/4" hex bar of 360 brass.

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Here is the location for the adapter. M12 x 1.00 threads.

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The first cut is about .700", which fits down into the groove at the top of the sight tube boss.

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Test fitting. It was nearly a perfect interference fit (just got lucky).

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Turning down the brass to 11.975 mm where the adapter will need to be threaded with the M12 x 1.00 mm die

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Test fitting the copper sealing washer. This washer will not only seal the pressure, but it will also serve as a shim to position the gauge in a forward facing position.

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Installing the M12 x 1.0 high speed steel die in the Taig's die holder. This holder mounts on the lathe's tailstock, which helps ensure that you are cutting perfectly square threads against the work.

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Here is a photo showing how the threading jig mounts up

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Ready to cut some threads (by hand). The lathe acts as a threading fixture, but you still turn the chuck by hand (so that you can control everything).

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Cutting away

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And here are the M12 threads

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After chamfering the leading thread a little

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Test fitting on the La Pavoni

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Here you can see the "adapter" completely threaded in

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Getting ready to center drill a starting hole (so that I can drill a passage through the adapter).

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Center drilling complete.

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Using a cobalt drill

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Done drilling the passage through the adapter

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A little detail work on the end of the adapter. I put a chamfer on the hole and a crown on the end (sort of like when you crown a rifle barrel).

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Here I have knocked down the tips of the 3/4 hex, in order to give the adapter a smooth flowing appearance.

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Just double checking how everything looks.

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Working on the top part of the adapter. I've cut a taper along the top of the hex (which gives it a nice look I think). I'm also turning a shoulder, so that I can part off the work and flip it around.

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So far so good!

(continued on next post...)

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RayJohns
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Postby RayJohns » Aug 10, 2011, 10:01 am

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Half way done!

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You guessed it... test fitting

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Getting setup so I can part off the adapter

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Parting off

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Here's the adapter, after parting it off from the main brass bar

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Checking to see how it torques down

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Not looking too shabby there! :-)

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Here I am using the drill to align the part and install it back in the chuck (on its original axis)

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Getting ready to drill the hole on the other end, so that I can tap the adapter to 1/8-27 NPT

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Almost ready to tap the hole that has been drilled

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Added a slight chamfer on the hole, in order to help the tap start a little better

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Using the tail stock to hold the 1/8 NPT tap

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The initial threads for the gauge

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Test fitting the gauge. As you can see, it sticks out way too far. This is because NPT threads are tapered, not parallel. The solution is to use a second pipe tap and grind it down (turning it into sort of a bottoming tap). Luckily, I just happen to already have one in 1/8 NPT, which I used to use when building motors.

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Here you can see the normal 1/8-27 NPT (bottom) and also the "bottoming" 1/8-27 NPT tap (top). The tap on top allows you to widen the hole, which will allow the gauge to thread further down into the adapter (for a nicer fit).

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Back to work threading - this time with the bottoming in pipe tap

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That's much better.

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Here you can see that I have put a shoulder around the inside of the top thread (to allow the gauge to seat down a bit better). I've also turned down the neck a bit, in order to give a bit of a separation between the hex area and the top part of the adapter, which accepts the gauge.

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Here is a side view, albeit a bit dirty

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Here's the finished adapter, after a little cleaning and polishing

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Test fitting.

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Here it is with the stainless steel pressure gauge installed (I used Teflon tape on the threads of course).

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The copper sealing washer had to be filed down, in order to correctly position the adapter and align the gauge in the forward facing position. The initial size of the washer was .050" thick; I had to take it down to about .045"

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Here's the finished copper washer on the adapter

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All done!

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Here's a shot of the gauge, now that I have the La Pavoni back up stairs.

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Here's a side view

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A close up, showing the final positioning of everything.

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Bringing the machine up to temperature, in order to pressure test the connections.

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No leaks whatsoever; it's nice to have the adapter finished and have the gauge back on the machine.

So, aside from a couple of very minor things that I still need to do to the machine (such as gluing back on one of the rubber feet, etc.), I think this basically concludes the La Pavoni PID project. It's been quite a project, that's for sure. Thanks to everyone who commented and provided input/suggestions on this thread... I really appreciate it.

When I have a second, I'll make a video of the machine in action (pulling a shot and making a latte).

The PID controller has made a huge difference. I know some people have commented that adding a PID controller to a lever machine isn't needed and/or that it's a waste of time. However, based on my experience(s) with this project - as well as using the machine before and after installing the PID controller - I can stay definitively that adding a PID controller makes a huge, huge (i.e. night and day) difference in not only the ease of use, but also in the consistency and quality of the shots. It's like having a whole new espresso machine.

Ray

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norby
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Postby norby » Aug 10, 2011, 4:54 pm

You're a real hero.
Thank you for this thread, it was fun to read it.

(Just one question: why brass, not stainless steel? )

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RayJohns
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Postby RayJohns » Aug 10, 2011, 8:38 pm

norby wrote:Just one question: why brass, not stainless steel?


My initial plan was to make one in brass as a test and then make the final one in stainless steel. However, there are a couple of issues to consider here, which caused me to settle on using just brass:

1. The primary reason is because the gauge, itself, is stainless steel. In my experience, especially when heat is involved, stainless to stainless threads can act a bit funny at times (or even stainless to plain steel). Especially when heat and high loads are involved, the threads can exhibit a very nasty habit of seizing to each other (to the point of practically brazing themselves together). Because this is the last thing I want to have happen on the La Pavoni, I decided to stick with SS against brass.

2. A hard metal tends to wear (and also seal) better against a soft metal. The wear characteristic are much better than when you have two soft metals or two hard metals against one another. Thus, again, because the gauge threads are SS, I felt using brass would probably work out better.

3. Turning and cutting threads in 360 brass is a joy on the lathe. 303SS isn't too bad either, but working in brass is really a lot of fun. Also, having the part in brass allows for a lot of hand finishing (using a file, etc.), without quite as much effort as it might require if the part was made from SS. Since this is a hobby and part of the reason I did the project, in the first place, was for the fun of it, I decided to stick with the brass and not turn making the adapter into a nightmare.

4. I think the contrast between the brass color and the silver of the La Pavoni is nice. The little accent looks good along with the brass screw that holds the machine together, as well as the brass on the naked portafilter. Stainless looks nice too, but I think the brass gives it a slightly "warmer" feel.

Ray

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allon
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Postby allon » Aug 10, 2011, 11:17 pm

Beautiful work!

Why not use a crush washer to get the alignment instead of filing down the flat copper washer?
LMWDP #331

norby
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Postby norby » Aug 11, 2011, 3:04 am

Brass vs. steel:

fair reasons, thanks. I never thought of this aspect (soft vs. hard) That's why you're doing this :)

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RayJohns
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Postby RayJohns » Aug 11, 2011, 3:14 am

allon wrote:Beautiful work!

Why not use a crush washer to get the alignment instead of filing down the flat copper washer?


Thanks!

Good question regarding the sealing washer:

I actually did try to use a copper crush washer, which I happened to have on hand from when Eric was nice enough to send me that first adapter for the machine. However, the problem was that it didn't crush down quite far enough to allow the adapter to turn enough. It stopped about a 1/4 turn from facing forward. As I recall, it crushed down to ~ .050" when fully compressed (the same size as the other copper washers, as well as the same size as the original La Pavoni "fiber" washer, which was under the block-off screw).

I was actually going to use the OEM La Pavoni fibrous washer, but I accidentally sanded it down too far (which allowed the gauge to then turn too far). At that point, I was running out of options, so I went back to using the solid copper washer and decided to just carefully grind/file/sand it down (about .0005" at a time) until the gauge tightened down into the proper alignment.

The other issue is that the crush washer is sort of a one-time shot. With the copper washer, it still effects a seal, but you can re-use it a bit more readily.

Ray

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novyan
Posts: 64
Joined: Mar 03, 2009, 2:43 pm

Postby novyan » Aug 11, 2011, 10:11 am

wow! like it was a factory PIDed! With all that machinary/equipment you have, you could build a whole new machine from scratch :), awesome!
LMWDP #343

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RayJohns
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Postby RayJohns » Aug 11, 2011, 10:27 pm

novyan wrote:wow! like it was a factory PIDed! With all that machinary/equipment you have, you could build a whole new machine from scratch :), awesome!


:)

That thought has actually crossed my mind. However, the La Pavoni is such a great (simple) design; I'm not sure I wouldn't be partially reinventing the wheel.

If I get that far into building something, I think it would more than likely be a high end coffee grinder actually. I've been giving some thought to maybe designing some sort of manual grinder, which would allow me to grind coffee beans (something very high quality and precision - like where you can adjust the burrs using a dial indicator or something. I think that would be something really nice to have. The Kyocera is great, but I am not totally happy with how the adjustment works. In fact, I have been thinking about making a little replacement adjusting knob for it.

We'll see. For now, I'm just going to enjoy using the La Pavoni for a while I think.

Ray

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RayJohns
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Postby RayJohns » Aug 12, 2011, 9:22 am

... and the saga continues :-)

I made a little fixture this morning, so that I could have a spout under my naked portafilter. Below is a photo:

the full write up is located here ----> Not so naked portafilter


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Ray