Studs instead of bolts for Pavoni group-to-boiler mount

#1: Post by **pcrussell50** » May 23rd, 2016, 5:09 pm

I just ordered a set of ARP stainless studs to put in place of the stainless Allen bolts I had already replaced the stock bolts with.

It may be overkill since hardly any torque is needed when the gasket is fresh, but since repeated disassembly is part of routine cleaning and maintenance, and repeated threading and re-threading is hard on threads, particularly brass, studs will stay in the brass boss, and only the nuts will need to come on and off the stainless studs.

I'll post up some pics when the studs arrive and I get them retrofitted to my 2000, pressurestat pre-M and my 2004 M-edition, Europiccolas.

-Peter

#2: Post by **rpavlis** » May 24th, 2016, 1:05 pm

I did this with the 1978 La Pavoni a while back. I measured the depth of the bore with a vernier caliper, and ran a bottoming tap down the bore first, and then installed the stainless steel stud cut to the correct length. I put an anti seize compound on it, I forgot which one. This is very very convenient. (The 1999 has brass bolts that I purchased from some place, I forget where, but they also go deeply into the bore. This is the all brass machine that I have gradually made even more brass than the original. The portafilter handle and the group handle are both brass, and I plan some time to make the group lever from brass too!)

May 25th, 2016, 10:03 am

Robert, when you ran your bottoming tap into your 1999, how much material come out? Did it appear that the assemblers at Pavoni had used a bottoming tap or a tapered/starting tap during manufacture?

-Peter

#4: Post by **rpavlis** » May 25th, 2016, 12:07 pm

I did this with a 1978 and a 1999. With one the bottoming tap went all the way in and simply screwed in without removing any metal. The other one removed a bit of metal for perhaps the last two or three turns. I was concerned about the metal at the end of the bore being thin, so I carefully marked the bottoming tap to be sure I would not run it into the bottom of the bore.

I cut the studs so that I could put an "acorn" nut on them with a washer under the nut and still tighten it properly.

I did not mention that I originally had the 1999 with stainless steel studs too, but I was on the "as much brass as possible" project with it and later got brass bolts for it. I still have the studs that I cut for it. I think they are in my box of miscellaneous espresso parts. (This is distinct from my box of servicing tools and parts.)

Before posting this, I thought others interested in doing this might find the length of the stud I used useful. I just dug one out of the box and measured it with a micrometer. I had cut it to exactly 25.00mm. With an acorn nut and a washer under it, that is perfect for both of the machines I have, but others may vary?

May 25th, 2016, 12:27 pm

rpavlis wrote:I did this with a 1978 and a 1999. With one the bottoming tap went all the way in and simply screwed in without removing any metal. The other one removed a bit of metal for perhaps the last two or three turns. ...snip... I just dug one out of the box and measured it with a micrometer. I had cut it to exactly 25.00mm. With an acorn nut and a washer under it, that is perfect for both of the machines I have, but others may vary?

Thanks Robert. I'll report back when I've completed mine regarding stud size. Based what I remember about the bolt length I used when I converted to stainless M6-1 Allen cap screws, your length sounds compatible with what I got. I'm away from my machines right now, so I can't pull out the stainless cap screws and measure. I'm relying on memory. But I made sure they were long enough to use almost all the depth of the threaded boss on the boiler.

-Peter