I think if it were me, I would maybe use brass washers on the inside and copper on the outside, or something along those lines. I don't know if the O-ring approach is going to seal all that well - at least based off what I can see from the photos.

Another option might be those washers with the O-ring inside them. Not my first choice, but it might be something to look into. It's sort of a metal ring with a rubber center. The other option might be some sort of hard fiber gasket/washer.

Ray

I haven't been following this thread just a quick browse this morning, I noiced the posts re element seals. I bought some of the correct element gaskets from a local element manufacturer, just a stock part, I think they even gave them to me, so rather tham improvising try contacting a elememt maker, hope this helps.

Thanks, all. The Durometer is a high temperature, hardened silicone rubber stock that was recommended by Barb Garrott awhile ago when I was trying to cut a large gasket for the boiler. After that I was able to source a fiber gasket that had actually been manufactured for the Prestina, so I bought two.

Doug Garrott has recommended an item he has in stock for the heating element gasket. It's called an "Alimentary Gasket for 1/4" BPP Fitting" and it looks like this:



I'm improvising because Doug and Barb are at Seattle Coffee Fest and I thought I'd see what I could do with a punch set.

Two of you have recommended copper crush washers. Ray, nice to hear from you. You're suggesting brass on one side and copper on the other. You've recommended copper before. As a learning piece for those reading this, what are the advantages of copper or copper on one side and brass on the other over alimentary fiber, Teflon, Viton? And if you were to fabricate such a thing (I would try and order one online), would you need a lathe?

Lots of good suggestions so far.As vicroamer said, custom element places are very good and cheap.Here's another option i use sometimes.The cafeparts site has a search function.If you search under 'teflon gasket' you get lots of options, and sizes are most often listed.I spend hours on this site looking for parts to match old vintage levers.Whilst it may be a pain for small orders, i quite often just order lots of different sizes to have as spares for future projects

http://www.cafeparts.com/staticIndex.asp

From what I have seen, copper crush washers are used on pressure safety valves and fittings designed to seal against flat parts of the boiler. Heating elements usually use the alimentary material or Teflon but in a few special cases such as La San Marco elements which have a curved face at the end designed especially to use an o ring. I have seen brass flat washers used under a nut as a bearing but not inside on the heating element side. If an o ring can be used the fitting will have a shoulder under the fixed nut.
Copper crush washers are seldom used where alignment is an issue since they are not forgiving in nature...alimentary or Teflon are better in these cases.

drgary wrote: Ray, nice to hear from you. You're suggesting brass on one side and copper on the other. You've recommended copper before. As a learning piece for those reading this, what are the advantages of copper or copper on one side and brass on the other over alimentary fiber, Teflon, Viton? And if you were to fabricate such a thing (I would try and order one online), would you need a lathe?

I'm not 100% sure what you are attempting here. Doug mentioned a curved surface to seal against, which would probably let out cooper as a sealing washer. The only reason I mentioned brass on the inside was in case you wanted to avoid cooper or something.

Are these heating elements going through a boiler, which has a curved surface to seal against or are you tightening the bolts up against a flat surface?

On my PID La Pavoni, I was surprised how much clamping force was required to produce a water/pressure tight seal using the copper gaskets. If I recall correctly, I used a brass nut on the inside of the boiler, although I tried SS first. I would have to go back over the thread and check.

As far as fabricating something, if you are using silicone or rubber, then basically punching or cutting would be required. You might check into a punch die affair such as this:

http://www.amazon.com/True-Power-Pc-Pun ... B0010ZM6EW

Maybe not that exact one, but along that idea. You might also search "greenlee" punch or knockout kit/set on ebay or amazon. Greenlee punches are very high quality punches, which can cut through steel, etc. They are used in fabrication, etc.

As far as using the lathe: yes, that will work. You can face/turn your own washers from round stock, etc. However, it's usually just easier to buy them from some place like mcmaster.com in my experience. It just depends on what you need. Also, sometimes thickness becomes very critical. On my machine, for example, I had to take a washer down .0005" at a time in order to get the pressure gauge to sit exactly forward (when using a solid copper sealing washer).

The other thing you might consider here - depending on how much free threads you have to work with inside - is a custom made washer that has a machined groove on the underside, which will index an O-ring up against the surface. The nut on your fixture there would press down against the washer and then the washer would trap the O-ring in a groove.

Also, what about filing or machining down the surface a bit so it's more flat than curved? Either that or maybe TIG weld a very thin boss? Just something to give you a flat surface to work with. On my La Pavoni, for example, I had to hammer down the front curve of the base (very slightly), so the PID controller matted up against a flat surface, instead of a very mild radius.

Just some ideas.

Ray

try searching "sealing washers" on mcmaster.com - check out the pressure-sealing washers and/or the metal bonded washers. Polyurethane might be another option.

Ray

Thanks, Ray. I asked because you always have interesting and precise ways to think about these things. There's no curved surface to seal against unless you consider the tubular shape of the heating element end. But the boiler surface is flat, pretty straightforward. I was fooling around as a hobbyist while waiting for Doug and Barb to return and having them send me what I need. His post above seems definitive for this purpose. Since I have a Viton sheet on order and some punches I'll give that a try first. The main deal will be getting a tight fit on the steam and water taps so these don't turn. I've actually started a How to Cut Gaskets? thread for this kind of discussion in general. This Prestina restoration and the fitting of a Teflon group to boiler gasket on my Elektra Microcasa a Leva prompted that thread.

I bet you dollars to hand cut donuts that the water and steam bodies will be pretty close to being aligned properly when you tighten them down. I would guess that teflon or alimentary will be the gasket here to use since they can both squash a little to get the alignment right without a lot of teflon tape fol de rol. What is the plan for the viton? I only use viton sheet to make Peppina washers and Microcimbali disc valves. Pretty spendy stuff for a boiler gasket, and a little soft as well. Get a sheet of alimentary...the green stuff...hard to work with but good for boiler, group to boiler, lots of flat work....really the right stuff as far as that goes if you can tool up to work with it.

drgary wrote:Thanks, Ray. I asked because you always have interesting and precise ways to think about these things. There's no curved surface to seal against unless you consider the tubular shape of the heating element end. But the boiler surface is flat, pretty straightforward. I was fooling around as a hobbyist while waiting for Doug and Barb to return and having them send me what I need. His post above seems definitive for this purpose. Since I have a Viton sheet on order and some punches I'll give that a try first. The main deal will be getting a tight fit on the steam and water taps so these don't turn. I've actually started a How to Cut Gaskets? thread for this kind of discussion in general. This Prestina restoration and the fitting of a Teflon group to boiler gasket on my Elektra Microcasa a Leva prompted that thread.

If it's a flat surface, then I think I would use copper washers myself. Just be careful that you don't apply too much load to those threads and break your fittings there. The other option would probably be some of those washers on mcmaster.com. Another thought would be to use O-rings and then machine a washer which fit outside of the rubber O-ring and sort of keep it from squishing out.

In my opinion, it's difficult to beat copper washers when it comes to mechanical sealing.

Ray