Re: Rancilio silvia grouphead screw mod where to buy?
OK, to finish this thread (for me at least) there appears to be two different mods to improve the problem of the big hex head causing channeling issue. The simple one (that Ive done) is a straight substitution of a SS 5x15mm button head screw for the original hex head. The complete mod is to substitute it with a countersunk screw, which involves some relatively straightforward fitting/adjustment in a vice. Its obvious to me that the simple mod should go a long way to removing the potential channeling issues. For those who demand complete certainty, the complete mod is the right solution.
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Re: Rancilio silvia grouphead screw mod where to buy?
Richard - since youve got a machine-engineering background Id assume you have a vice. The showerscreen (if yours is flat like BBs was) should be able to be formed by countersinking the jetbreaker button and then using a vice, the jetbreaker and a C/S screw as a former.. (plus maybe a socket for the end of the screw to sit harmlessly in).
Thats what I was going to do until I realised mine was already countersunk!
Granted, stainless is hard and gnarly stuff, but your average 4" dawn vice will make mincemeat of the problem :
A slightly better thing though is to use a countersunk former that is marginally bigger than the machine screw head. Something like an 8g or 10g maybe C/S woodscrew?
I cant help but think that on my Silvia there was at least the intention of putting a countersunk head in there - otherwise why would they have used the countersunk button? (Thinks to self: because they had a warehouse full of M5x12 hex bolts
)
/Kevin
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Re: Rancilio silvia grouphead screw mod where to buy?
I now have a supply of 15mm x5 buttons, countersunks, and 12mmx5 countersunks, so I can see what works best. I probably over-ordered. I think the main killer with the existing head is its sharp-edged hex corners and especially its wide screwdriver slot which must inevitably cause some wild cross-currents under hydraulic pressure. Im now disinclined to put the shower screen under any kind of pressure by pressing a countersink. My earlier days as an aviation instruments techo make me think theres a chance this cure might be worse than the disease. Just putting a smaller head round with no slot must help any tendency towards channeling. What do I do with all these damn screws?
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Re: Rancilio silvia grouphead screw mod where to buy?
My Jetbreaker was flat (2010 Silvia V3), nothing like KJMs so I had to countersink it and press the screw into the showerscreen.
If you do countersink, you must use a countersinking tool, or use a drill that is correctly modified to do the job. Normal drills do not have enough angle to countersink correctly (and may cause some of the problems mentioned above).
I initially changed to a SS button head screw (a 25mm one carefully cut down to about 14mm of thread) but I didnt think this made much difference to Silvia.
Mostly I did the mod so that I could get the portafilter on when I had filled the basket with "my dose" which is now about 22grams in an after-market large double basket. It was never really about channeling, although it no doubt helps.
BB
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Re: Rancilio silvia grouphead screw mod where to buy?
The Jetbreaker on my machine is already counter sunk. I dont know if it is a random variation, but my sisters machine is the same.Originally posted by 272D2C203529410 link=1296308711/34#34 date=1302949203You need to countersink the jetbreaker.
I just screwed it in, the stainless screen conforms to the countersink nicely - although if I were to be a bit more anal about it, Id probably kiss the countersink off a bit. I could make it even flatter when screwed in, but wed be talking a fraction of a mm.
I suspect you need to check your own Silvia and just see if it does indeed need to be drilled. There isnt much meat on the little button the screw goes into, so you cant countersink it much. I hope the photo illustrates what I mean - screen, button and screw.
Again, if anyone is going to the Beanology event, Ill have some of those screws in the ute. Just let me know.
/Kevin

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Re: Rancilio silvia grouphead screw mod where to buy?
Thanks for the life-preserving warnings here; have removed the zinc plated and am awaiting arrival of SS 5Mx15 buttons. All this angst over a screw? Must have been on Shakespears mind when he named a play "Much ad about nothing".
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Re: Rancilio silvia grouphead screw mod where to buy?
Gday Richard....Originally posted by 607B717A736076737E737073120 link=1296308711/32#32 date=1302913815So I went to a local hardware store and bought a packet of 5x15mm zinc plated button heads.
Not a good idea to have Zinc or any other highly reactive heavy metal in direct contact with the Brew Water Path mate. Id switch to s/s ASAP...
Excerpt from a discussion re: Zinc ingestion....
"Zinc is considered a heavy metal, which means that it is dense and that relatively low concentrations of the element in the body may lead to heavy metal poisoning. The symptoms of zinc poisoning are similar to other types of heavy metal poisoning. Because of this, exposure to any type of heavy metal should be disclosed to medical staff.
If left untreated, or if a high level of exposure continues, zinc poisoning can be deadly. Exposure to unhealthy levels of zinc should be limited for all ages. Parents should keep zinc supplements out of the reach of children, as well as keeping their children away from contaminated soil and water. Other adults should be aware of their workplace environments, and should follow medical recommendations on zinc supplements. If living in a contaminated area, filtered water should be used and soil disturbance should be avoided."
Mal.
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Re: Rancilio silvia grouphead screw mod where to buy?
Oh and I wouldnt be using a zinc screw anywhere near a coffee machine. Stick to stainless only.
I got my screws from a stainless steel bolt and nut shop on the sunny coast. They where great, I could buy single screws and it was pretty cheap. I used them to replace all my San Marino screws with stainless. No more rusted screws for me!!
From memory there was a great thread on CG that had photos of the mod.
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Re: Rancilio silvia grouphead screw mod where to buy?
I used an M5x12 for mine when I had Lucy. With the countersunk bolt you have to include the head because it sits up inside the screen as vickypoint said.
When I made mine I put a socket behind the jetbreaker, and loaded it into my vice (socket, jetbreaker, screen, screw) and tighten it up slowly to make the screen fit the countersunk screw. My jet breaker was already countersunk.
To be honest I didnt find that it made a difference for me, it actually made things worse and caused channeling.
Maybe I should have played with it more. In the end I bought a non countersunk jetbreaker from coffeeparts to stop the shower screen from bending into the countersunk jetbreaker.
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Re: Rancilio silvia grouphead screw mod where to buy?
Please read my link in the earllier post. You need to countersink the jetbreaker. You also need to use the screw head to depress the screen. I simply used a small socket under the screen. I then put the screw into the screen and gave it a tap to form the necessary depression. When you tighten the screw through the screen fitting it will form fit. 5x12 will be sufficent if you countersink and depress the screen.Originally posted by 392228232A392F2A272A292A4B0 link=1296308711/32#32 date=1302913815Report time: the M5x12 screws arrived and they are way too short. I dont know if the year model of Silvia makes a difference, but mine is the latest V3 and the existing hex head has a shank length of 14mm, whereas the M5x12 has a shank length of 9mm. They both have heads that are 3mm thick. So if those who PMd are sure their existing hexhead screws are 12mm in shank length (ie: the threaded part) then PM again and Ill be happy to offload mine.
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Re: Rancilio silvia grouphead screw mod where to buy?
So you dont actually need a countersink drill bit / vice etc to do this properly with the flat screw?Originally posted by 727374390 link=1296308711/18#18 date=1302396989I did this a while ago, and there is no mod needed apart from replacing the screw. The little button collar is countersunk already, and just doing the screw up pulls the stainless mesh into the dimple nicely.Originally posted by 46414550404B47504B56240 link=1296308711/16#16 date=1302304603Hello all, has anyone modified their Silvia to take a countersunk screw?
Mind you, I got allen key M5 screws, so now I have a tinytiny raised hex pattern pimple in the centre of the puck!
/Kevin
I have a La Marzocco double basket that I bought with a Pullman tamper a few years back, and just locking in leaves quite an impression from the original screw before the shot. If I dose much lower the tamper bottoms out on the ridge, and I think Im dosing 20g+ (current scales only resolve to 5g unfortunately)
Probably gonna try a $12.95 evilbay special for some 0.1g jewellery type scales
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Re: Rancilio silvia grouphead screw mod where to buy?
Report time: the M5x12 screws arrived and they are way too short. I dont know if the year model of Silvia makes a difference, but mine is the latest V3 and the existing hex head has a shank length of 14mm, whereas the M5x12 has a shank length of 9mm. They both have heads that are 3mm thick. So if those who PMd are sure their existing hexhead screws are 12mm in shank length (ie: the threaded part) then PM again and Ill be happy to offload mine.
So I went to a local hardware store and bought a packet of 5x15mm zinc plated button heads. While not as flush as a countersunk screwhead, they have a better overall profile and do not have the huge screwhead channel and 8 corners that are on the hex head. I decided Id rather not create a countersink in the shower screen for fear of distorting it. While zinc plating is reasonably rust resistent, stainless is better so Ill order some of the correct length but with a flathead profile. You can see the difference in profile between the hex and a button head in the pic below.

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Re: Rancilio silvia grouphead screw mod where to buy?
If there is any interest in this, I can bring a half dozen or so M5x12 CS machine screws along to the Beanology event.
Fellow CSers are welcome to them, M5 is not a pitch I used much at all.
Let me know. Ill endevour to not forget them!
/Kevin
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Re: Rancilio silvia grouphead screw mod where to buy?
Your explanation and pictures are soooooo helpful Bean Bear; thank you.
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Re: Rancilio silvia grouphead screw mod where to buy?
Frankenbolt = original hex bolt. When this is removed the showerscreen and jetbreaker (thats what Rancilio call this part) will also come off with it, they can be a little bit fiddly to put back on so be patient. If you are using the pictured screw you will need to use a countersinking bit to make the recess in the Jetbreaker so that the screw will sit flush with the shower screen. I would press the screw into the showerscreen and jetbreaker as shown in the link (using a vice).
Good Luck, BB.


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