Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 42

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
coelcanth

#411: Post by coelcanth »

if you do not have a thread gauge,
you can take a bolt with a known thread
and lay it on the thread of the fastener you are checking.

if they are the same threading they will nest together perfectly..
the diameter does not matter.

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drgary
Team HB

#412: Post by drgary »

Oh, you mean like this? Just got back from Home Depot, where I'd just done what you suggested. Great minds ...

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@ Tom: Really close but it takes the time it takes when you get right up to that point and can't fit a part. The essence of restoration is patience. It's also nice to have four other working espresso machines at home. :wink:
Gary
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What I WOULD do for a good cup of coffee!

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drgary
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#413: Post by drgary »

In my search for materials I'm having a very difficult time finding something that will work for the drip tray grate. I think I have the edging sourced. But although companies post nice looking patterns, to find this in the right size, small quantity, in type 304 stainless steel has come up negative so far. If anyone has an idea of a supplier I would love to know. What I'm seeking in the most basic material is a diamond pattern expanded design, either flat or raised with a LWD (long way design) length of about 0.400 and SWD of about 0.300. My Isomac Amica has just this material in its drip tray grate. The other challenge is buying a small piece, about 1 to 2 feet square.

Find perforated stainless is equally difficult if one wants anything other than boring round holes. I've tried Grainger and McMaster-Carr and no luck so far. I'm trying to avoid fabricating something myself by hand because the best I'll be able to do is round holes. Stainless would be too difficult for indented holes. Then I would probably have to go with aluminum and then have it chromed. That seems tedious and expensive.

So, casting my hopes out to your collective wisdom, are there any sources you can recommend?

In terms of what would be great to fabricate, I found an old Faema drip tray photo that has square holes cut in the steel. That would look just great on the Prestina.

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Another great look is this Synesso drip tray grate:

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Gary
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What I WOULD do for a good cup of coffee!

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drgary
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#414: Post by drgary »

On second thought, the easy availability of stainless steel sheet guides me back to wanting to make a close reproduction of the original Conti Pristina drip tray grate. I believe that can be easily fabricated.
Gary
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What I WOULD do for a good cup of coffee!

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drgary
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#415: Post by drgary »

Sightglass Installed

Moving along, I just finished installing the sightglass. I'm enjoying learning how this machine was designed. The sightglass is held in place by rubber gaskets that are pressed by brass washers above and below and compressed by a nut. The sightglass length is not precise but just needs to be long enough. I installed the old, longer sightglass, but I'm sure the replacement that's 1 1/2 inches shorter would work too. Added: The shorter sightglass is for this machine. The longer sightglass is for an Olympia Coffex/Maximatic or Cremina. Both work, so by mistake I installed the longer sightglass and had to get a replacement for my Coffex. Oops!

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Here are the washers that fit inside each end. They insert in this order, with the thin copper one at the bottom of the fitting, then the rubber gasket, then the thick copper washer. I lubed the rubber one with food safe petroleum lubricant.

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When the sightglass is inserted it fits loosely until the fitting is tightened down. But I left it loose to attach the fittings on each end. Then I tightened carefully until it was held in place. If it leaks after startup I can gently tighten it further. I'm glad I have a spare!

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The bolts for the fittings are M5, .8 pitch, 16mm long. I slathered each with anti-seize compound and used a #10 brass washer against the fitting. Here's where it can take a little time. Some of the old bolts had rusted so badly I discarded them and made a trip to Home Depot today to obtain replacement bolts and brass washers. Maybe next time I'll be more organized in the teardown to catalog and obtain the replacement parts in one go.

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Next I'll build the pipe that positions the PSTAT and will connect everything to the water tap. Erics has kindly sent me parts to complete that assembly. He also advised me to hook up a pressurized tank that will allow refills without starting a loud FloJet pump each time.
Gary
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What I WOULD do for a good cup of coffee!

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orphanespresso

#416: Post by orphanespresso »

Gary...I may have missed it, but shouldn't there be some kind of seal between the body of the sight glass housings and the boiler? Teflon or alimentary or even an o ring?

Another thing...measure the OD of the sight glass tube so if need be you can get some tube stock and cut your own glass. Plain glass will work with a floatie ball as well as the red line glass. You might want to use a floatie ball anyway since they are easy to see.

Good that you 86'ed the teflon pstat tube for hard copper.

I know that you have expressed a disdain for round holed in the drip tray but there is a fairly simple way to make a drip tray. You can use an aluminum or even stainless steel cake pan (the best the bottom of a springform pan or similar) from a thrift store and lay out a punch pattern and punch the holes with a center punch. If you punch against a soft material like a plastic cutting board it will produce enough curved surface on the hole to make the thin material increasingly strong to hold the shape and support weight surprisingly well. If you have an inexpensive arbor press you can make these quite simply vs high end perforated metal. The grate below has a layer of copper flashing applied to it with adhesive.

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For a water source, why not a good old garden hose? You can set it up with a quick fit right in the garden section of Home Despots and temporarily quick plumb to a faucet as well. No noise.

Just some thoughts since I did see the start date on this post....

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drgary
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#417: Post by drgary »

Hi Doug:

Thanks for checking. Awhile back I went through all that fuss about Viton, Buna, etc. Back then I cut gaskets to go behind the sightglass housings. Here's a photo:

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This is .07 Viton. It replaces an o-ring that protruded the same amount and is a bit more raised than the photo appears. I've also tightened the housings pretty well without overdoing it. The sightglass outer diameter (OD) is 10mm for others seeking one. As you can see above I have an extra.

I've jettisoned the Teflon PSTAT tube for 1/4 inch soft copper I bought in a hardware store, if that's okay. Let me know if I should use something different.

Thanks for the tips on the drip tray grate. I may be able to source a Synesso grate from one of their older machines and would cut that to size. Since I don't have an original Prestina grate, might as well improve on their original design. So, either I'll do something like this crude original:

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Or I'll cut a piece from this and edge it:

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I've already ordered the accumulator tank and pressure gauge based on advice of erics. These weren't expensive.

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I can attach the Ulka vibe pump from the Coffex I'll restore next since the FluidOTech pump I bought from you will replace it. I do have a FloJet at the ready.
Gary
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What I WOULD do for a good cup of coffee!

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RayJohns

#418: Post by RayJohns »

drgary wrote:Oh, you mean like this? Just got back from Home Depot, where I'd just done what you suggested. Great minds ...

<image>

@ Tom: Really close but it takes the time it takes when you get right up to that point and can't fit a part. The essence of restoration is patience. It's also nice to have four other working espresso machines at home. :wink:
Gary,

Keep in mind, even without a thread gauge, it's pretty easy to determine what kind of bolt you have - especially if you already know you are dealing with metric hardware.

You just need a metric ruler basically. Measure across the diameter of the bolt. Standard sizes are M6, M8, M10, M12. There are also M4 and M5.

Most M6 are 1.00 mm thread pitch.
Most M8 are 1.25 mm thread pitch (although there are 1.00mm also)
Most M10 are 1.5 mm, but there are also 1.00 and 1.25 mm

Those are the common sizes in general (for metric).

It's easy to figure out if you are holding an M10 bolt (10mm diameter bolt) - if it's 10mm across, then it's M10. But how do you determine the pitch? That's also easy.

A metric thread pitch of 1.25 means that for every one revolution/turn of the bolt, it advances exactly 1.25 mm in the hole. Said another way, that means that the crest of each thread is 1.25mm apart. As such, if you are dealing with a bolt that has a 1.25mm thread pitch, then if you measure the distance (using a small metric ruler) across 10 thread crests, you should have a distance of exactly 12.5 mm (crest to crest on the thread peaks). Simply measure with a ruler and you can figure out the pitch.

If it's a 1.5mm pitch, then 10 threads would span 15 mm or 1.5 cm. A pitch of 1.00mm would span 10mm across 10 threads. If you could 20 threads, then it would be 20mm for a 1.0 mm pitch, etc.

It's the same basic idea with SAE bolts. In other words, 1/4-20 means the bolt diameter is 1/4 inch and there are 20 threads per inch. So if you measure 40 threads (crest to crest) on your bolt, you should end up with a span of exactly 2.0 inches (because it's 20 threads per inch).

Having a thread gauge is much more handy, but using a digital caliper or even a machinists small metal ruler is another method that should produce results.

Ray

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drgary
Team HB

#419: Post by drgary »

Thanks, Ray. That's a great reference.
Gary
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What I WOULD do for a good cup of coffee!

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drgary
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#420: Post by drgary »

Synesso sales manager Ann Halsne has kindly offered me this drip tray from their old design machines at a very compassionate price. Its depth is 7 inches and the front curve can be bent back. It already has an upward bent back lip. With edging added this will make a better drip tray than on the stock Prestina. It will be the basis for the new drip tray fabrication.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!