I have a Gaggia Factory boiler cap that had an unfortunate encounter with my floor this morning. The plastic knob cracked and broke in half. I think the 15 year old plastic was pretty brittle after all of the cyclic heating that it's had. Anyway, a new boiler cap is $50, and the only thing that is broken is the plastic. The rest of it works fine, and a 17mm open end wrench will do for the moment.

I'm looking for ideas to replace the knob. Are there any knobs made to fit a 17mm hex? Since this knob lives under a chrome cover the aesthetics aren't important.

Thanks,

Jerry

Here's a photo of the cap with the broken plastic knob:

What is the specification of the threads of this cap? The Europiccolas and Professionals with the second and third generation groups use M32x2.0. Dies are available in that size. You can also install a wooden top to a brass base very easily if the brass base be thick enough. You need a piece of ultra hard wood to do this best. You can get a piece of brass, thread it, and drill and tap holes in both the wooden cap part and the brass part. After being certain that the threads on everything are correct and that you can screw the pieces together, get some very high quality epoxyresin and fill the holes in the wood and the top with it and then screw them together, being sure that there is enough epoxy so that when they are tightened together there is no space between the brass and wood. I might have a small scrap of ebony, I will give it to you if you need it, if I can find it. If you attach a metal cap it gets too hot to handle. (Though perhaps grade V Ti might be a poor enough heat conductor?)

I have seen some strange sockets to tighten things in small spaces with knobs on them. That would also be a solution should you be able to find one in 17mm.

The threading isn't really important because the cap is fully functional with only the exception of the knob on the top. A 17mm socket with a knob on it would be a good workaround.

I like the idea of using hardwood to make a new knob. I have a scrap of cocobolo that might be hard enough. I would just drill a hole in it, and use a chisel to fit it to the hex shape of the top. I think leaving it open at the top would be a good idea too since the OPV is built into the boiler cap. The steam release from the OPV may be partially to blame for how brittle the plastic became.

As always, thank you for the guidance.

Sugru is an option. It wont get hot to the touch, its hand molded and made mostly of silicone.
I use it for lots of broken bits- it also makes for a nice grab knob on a steam wand that gets hot.