After a full day of torching the studs and a lot of penetrating oil, I was able to successfully remove only four studs from the boiler of my Conti Prestina. The rest of the day was spent drilling carefully. The good news is I successfully got the boiler opened up with losing only a small amount of brass threads. It is amazing how well fused these two metals became over the years.

I am debating whether or not it is needed to re-thread this boiler and flange. I have dove deep into MANY posts on restoring these machines, but still cannot find any clear advantages to having threads. I don't understand why regular bolts with a head, washers, and nut aren't sufficient? Threaded studs would not allow the two pieces to compress as well in my opinion. Thank you for any input.

Here's my take. Threads provide more secure attachment where the threads grip the boiler flange and end plate along the shaft of the inserted bolt. Tensioning is then done by tightening a nut against a washer with a torque wrench. So, essentially, threading functions as a fail-safe device if nuts become loose. You would then have a leak that calls your attention to the need to re-tension the bolt(s) by tightening the nut(s). Routinely during break-in of a new boiler gasket, you'll be tightening the bolts until the gasket is deformed as far as it will go, filling some imperfections in the flange and end plate.

When I tapped new threads in my Prestina I was restoring the original design. From my old restoration thread, "all the bolts with a raised surface on the face plate were threaded." Those are the ones I re-threaded. So, Conti's design had only some of those bolts implementing this safety feature.

Here's that discussion:

Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed)