Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 23

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

#221: Post by drgary »

I'm also planning gasket replacement, and there are many gaskets in this thing. So before chipping away the remnants of a gasket I photograph it. If you look closely at the part on the bottom you can see a corroded rubber gasket where the threaded tube meets the hex part. I will measure these with calipers where necessary for reordering. Fortunately Orphan Espresso carries some of these matched to the parts.

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I'm also planning final cleanup of these parts and trying to determine whether I should hand clean them with Barkeeper's Friend (a cleaner) and steel wool or whether an ultrasonic bath is necessary to do the job right. The two photos on this post show the residue that remains after the acid bath and thorough rinse.

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Tomorrow I'll go over to Grainger with what remains of the rusted bolts and with the boiler. I'll size the bolts and order them.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

jonny

#222: Post by jonny »

Gary, I used a wire wheel in my drill propped up to finish the princess' parts along with some steel wool for tight spaces. It worked quickly and effectively. I am very pleased how they came out. Check them out on the last page of my thread.

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drgary
Team HB

#223: Post by drgary »

Thanks, Jonny. That parts look sparkly clean in your thread.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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TomC
Team HB

#224: Post by TomC »

I've thought a lot about buying an ultrasonic cleaner, figuring it would cut the elbow grease factor down quite a bit. There's plenty of cheap ones made for jewelry, but those would likely be way to small for the larger parts.

I still like the idea of having one of Dougs polishing bead bed things that you can toss your parts into and pick up a sparkling beautiful part the next morning, no elbow grease required.

This is quite a project you've got, but I'm sure the results will be well worth it. The pride of ownership must be phenomenal when you know all the ins and outs of the design. I feel the same way about my project and it pales in comparison to what you've got on your hands.

Fingers crossed I can get pick my gear up from the powder coater tomorrow. I also found a metal plater I might check out.

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RayJohns

#225: Post by RayJohns »

What? Gary.. you don't have a CNC water jet yet?
Just cut yourself a copper sealing gasket and be done with it already

:)

Ray

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drgary
Team HB

#226: Post by drgary »

jonny wrote:Gary, I used a wire wheel in my drill propped up to finish the princess' parts along with some steel wool for tight spaces. It worked quickly and effectively. I am very pleased how they came out. Check them out on the last page of my thread.

For those following this thread, the restoration is moving forward even if I got a little distracted adopting a vintage Elektra MCAL. :lol:

I'm almost through doing as jonny suggested, polishing up the bronze parts and most are now shiny clean. I've also been sourcing parts and have been offered an original Prestina fiber boiler gasket. In offline conversation Ray Johns had also suggested I consider fiber, so that's the way I'll go and without all the missed cuts and punches. I'm also completing my list of fasteners and other parts complete to move ahead with the rebuild. For now I'll assemble this machine with brushed steel panels and get it up and working. But when time permits I may take up DJR on his offer to use his large buffing motor and bring those panels back to a mirror finish after I've had a chance to go over them with finer grit sandpaper in preparation. He suggests moving up to 600 grit. So although there are no new pictures to show, it's happening slowly but surely. :wink:
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#227: Post by drgary »

The nuts and bolts of hardware selection, gathering opinions

Hi Folks:

I'm talking with the experienced repair tech who's helping me source parts at Allann Brothers, and he suggests boiler bolts that are not stainless steel because the non-stainless is harder. He's also suggesting I use steel nuts to fasten them.

Reading Paul Pratt's Gaggia Orione restoration I saw that he prefers stainless steel bolts and brass nuts. But the guy at Allann says brass is very soft and these different metals when paired tend to fuse.

Here's the quote from Paul:
Paul_Pratt wrote:I think page 7 has a comment from John about this and he says he had a bad experience with a steel stud and a steel nut. He also said Kees is now using brass nuts on steel studs, IIRC the GS3 also uses this as well. After doing a bit of googling, it does make sense that the threads on the steel parts could bind (thread galling) together due to a number of factors. This was quite useful.

http://www.estainlesssteel.com/gallingofstainless.html

The gist of it was that when you tighten the steel nut and steel bolt, you remove some surface metal of the threads when they contact each other which may cause trouble later. Another site I read recommends some molybendum grease to prevent the thread galling.

The reason I have no problem with using the stainless studs and a stainless nut is because the studs can be screwed out from the brass boiler anyway. So even if the nut and the stud became stuck it would just screw out the stud.
In either case I would coat these fasteners with a lubricant. Paul is suggesting molybdenum grease. I was thinking of using something like Dow111 silicone lubricant to help prevent the rusted, frozen bolts you've seen me struggle with earlier in this thread. I'm interested in others' opinions on this. What do you think?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#228: Post by RayJohns »

Steel nuts, steel bolts, copper anti-seize. That would be my suggestion. Buy something high quality from http://www.McMaster.com

You can also use titanium hardware (with copper anti-seize), but good quality titanium hardware is difficult to find and rather expensive when you do find it. I use titanium on my street/track bike to save weight, but it's not cheap. I buy all my titanium hardware from http://www.pro-bolt.com in the UK.

I would recommend against stainless steel when heat is involved. Stainless has a bad habit of brazing itself to things when you least expect it. Stainless also generally isn't quite as strong as good quality steel hardware. Stainless loves to fuse to other metals if heated up (even just the friction of torquing down the bolts can do it). Stainless can gall. If something goes wrong with stainless threads (i.e. they fuse), you are screwed - literally. Generally the only option at that point is to break the nut off the bolt by twisting things until something snaps or to drill the bolt out, etc. If enough heat is generated or involved, stainless will basically weld itself to steel threads. I had this happen to me once and I never was able to get the stainless bolt out; I had to take my torch and just cut the section of steel out and weld a replacement part back in place. The part with the stuck stainless bolts/nuts ended up in the recycle bin.

You could use brass nuts (or even bronze or copper) to steel, but I think due to the pressures involved, I would stick with steel to steel myself.

Speaking of titanium hardware, some just came in the other day (for my front suspension on the motorcycle). If you want to see what $80 US buys you, check the photo below...

Ray

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drgary
Team HB

#229: Post by drgary »

RayJohns wrote:If something goes wrong with stainless threads (i.e. they fuse), you are screwed - literally.
:lol:

Thanks, Ray. Steel on steel it is.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#230: Post by drgary »

Picked up boiler bolts, nuts and washers on Friday at a local hardware store, grade 8 steel, metric size 8, fine pitch (.125) like what was removed plus a Craftsman torque wrench and ordered food grade Loctite anti-seize compound online. Starting to get excited that completion is in sight.

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Added April 7, 2013: After disassembling the boiler to service the taps I discovered the longer bolts that connect through the frame had started to rust after only two months in service. I am now ordering marine grade (316) stainless steel hardware to replace these choices. Both bolts in the photo were coated in anti-seize compound. The longer bolt was exposed to some water in early leak testing so the shorter bolt might also not have held up over time. Penny wise ...

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!