As I assemble gaskets and such for my vintage Conti Prestina I see that I may need a few gaskets. I've got a source and can probably solve that. But it got me thinking how useful it might be to become equipped to cut some of my own. This also became apparent when DJR gave me a group to boiler gasket he'd cut for his Elektra Microcasa a Leva (MCAL). Now the group is temperature-stable. The MCAL has an o-ring portafilter gasket that is prone to dropping out and I would love to replace it with a square cut gasket, but there is no such product. It would be nice to buy a thick rubber sheet and cut one.

Here's what I'm finding so far and would love to hear from those more experienced in restoring and servicing espresso machines. What materials and tools do you like? What's do-able on a budget? What cutting techniques do you use to cut accurately and safely?

Materials

I've come across several choices of gasket material. With my Prestina I've sourced the stock fiber gaskets for the boiler and group to boiler. That saves a lot of work and they aren't expensive. When they get baked, they chip off. Also they're not going to provide insulation the way a Teflon gasket does. And they won't expand to fill gaps the way rubber might do.

There are high-temperature, hardened rubber materials. Awhile back I bought some high temperature Durometer sheeting at McMaster-Carr and tried to cut a large boiler gasket as suggested by Orphan Espresso. I fumbled the job because I was free-handing it and didn't take enough care. I bought a square foot sheet 0.125 inch thick for $27, which seems expensive. It also hardens over time but for applications where that matters it probably offers some insulation. It will fill small gaps. It can be easily cut with a scissors or hobby knife. One can also easily punch holes in it with a leather punch but drilling creates a ragged edge.

Then there's Teflon, which I think is generically PTFE plastic. This material is more durable than the first two. The material is harder and compresses less easily. It's also harder to cut thick sheets. But I haven't worked with Teflon and would love to get others' impressions.

If there are other materials useful for our purposes I'd be interested to know. There are sub-grade solutions like the one I found on my Olympia Coffex machine where someone had used automotive gasket compound on the boiler. This stuff isn't food grade, so that alone should rule it out. But are there gasket compounds worth considering? This doesn't seem to be the way expert restorers do the job, so it's probably not the way to go.

Tools

There are simple tools for free-handing it, but that's risky. I've already destroyed some expensive material trying to free-hand a large boiler gasket after not tracing it carefully. I used a hobby knife and scissors can also be used.

I've seen circle scribing tools online. Some seem like they may not be rugged enough to cut through thick or hard material. What would you need, for instance, to cut 0.125 inch Teflon? I also found an industrial grade metal product that seems to mount on a drill or drill press. The circle cutter itself isn't expensive but it seems dicey to use. There's a heavy duty model for use on a drill press, which should offer more control but adds cost over using the hand drills most of us have at home.

Here are two inexpensive OLFA circle cutters I found on Amazon. They seem to be light duty but the smallest compass cutters may work for very small gaskets. I haven't tried these so wouldn't know which model to recommend for cutting specific sizes and materials. That's one of the reasons I'm posting this.





There's a cheap X-Acto compass cutter that may work for small gaskets that I haven't pictured here.

Then there are industrial grade tools and those pictured here aren't much more expensive than the hobbyist tools I just showed you. These were found on a National Supply Source site that then links you to your local distributor. The first is a washer cutter that is described as able to cut leather, rubber, cork, graphite, fiber, copper, and other soft materials. It fits into a bit brace or a hand powered drill only, will cut inside and outside diameters simultaneously and costs about $18.



They offer a variety of these that goes up to something like this, a heavy duty circle cutter. It cuts sheet metal, brass, copper, soft steel, aluminum, plastic, wood, and composition materials. Depending on size this tool costs from $20 to $42 and seems like it would work in a power drill or drill press, but that isn't specified. In a similar price range they offer a heavy duty model that works in a drill press.



I bought a leather punch kit on eBay that I've used to cut holes in hard rubber. This can also work for at least the thin Teflon sheets. It's easy to use. One places the material on a cutting surface and drives the hole with a hammer.



Moving up from here, do people use wood lathes or other such tools?

Before you go hog-wild here, people do sell square-section O-rings. Call around to bearing shops.

Best,
David

David:

Thanks for that suggestion, which may be a good way to go. BTW I'm not posting this because I'm unable to find gaskets. I was curious about what's needed to make some that are harder to get and whether it can be done quickly and inexpensively when one is right in the midst of a restoration or repair. Apparently the answer is yes. Mostly I'm curious to see how it's done.

A trick we have used frequently for cutting gaskets at work (I am an Aircraft Structural Repair guy in the USAF) is to get an appropriately sized piece of tubing if we are cutting round gaskets. Stainless tubing works best. you just sharpen the edge with a file and clean it up with some sand paper or honing stones. then line up and WHACK it with a big ol hammer. If you back up the gasket material with a block of wood (end grain works best) we usually get a clean cut clear through in one good shot. bigger the hammer the better. Of course this only works on round gaskets.

I was wondering how to cut gaskets bigger than the punch sets. There you go. Get a bigger gauge of stainless steel tube. Thanks!

yeah, that technique works like a champ. of course it does not have to be a piece of stainless tube (aluminum or even mild steel pipe like you would use in plumbing will work), however neither will cut as clean or stay sharp as long.

BTW I found an inexpensive leather punch set on eBay that goes up to 3/4". Several vendors are selling it, so I ordered one. Cost delivered will be under $12.

Has anyone tried circle cutters like the ones above?

Doug Garrott told me another method is to buy a rod of material, cut it and then use a punch, or to buy silicone tubing, fit it around a dowel and cut it. He says 3/16" Teflon can be cut fairly successfully but is harder to work beyond that thickness. On my Conti Prestina rebuild thread he says this about getting material that is properly heat rated:

orphanespresso wrote:HNBR and NBR sound a lot like designations for BUNA rubber. The lowest temp rating available. The material should be at least EPDM, HSEPDM, Viton is best (silicone has a higher temp rating but is often too soft for some applications). I have never seen BUNA used on an espresso machine unless it was sourced at the Home Despot by someone who did not know any better.