by RayJohns on Sat Nov 19, 2011 11:17 am
Looks like you have some scaring on your group head cylinder there?
On the portafilter size, the older machines (like what I have also) should be 49 mm. Later on, they increased the size to 51 mm.
The best way to match the tamper is to measure your actual portafilter basket with digital calipers, in order to verify size. However, in my experience, if you have a 49mm basket and you want a very tight fit around the edges (as you tamp), then 49.6 mm is just about perfect. 49.7 will not allow the tamper to go down far enough and it will often jam up on the sides as you are tamping. 49.6 will work almost perfectly, but you may need to take some very fine sand paper and take just a very slight amount of material off the diameter to allow the tamper to move more freely.
49.5 mm should work no problem, but it may be just a hair loose (if you are trying for a super tight fight around the edges - especially if you tend to load up a lot of coffee in the basket). Keep in mind also, the walls of the basket are a bit more narrow further down, so if you are using a tamper that is a very close fit, it's probably going to only go down about 3/4 of the way.
49.5 or 49.6 is the way to go in my experience.
If you are looking for a tight tamp around the edges, then a 48.0 mm and 49.0 mm tamper are both pretty much worthless. It's not until you reach 49.5 mm that you really will be able to produce a perfect tamp around the edge. 49.7 will be too big. 49.6 falls right in the middle and is very good (and what I use here), but just keep in mind that it will be a very snug fit and you probably will have trouble spinning the tamper at the end (unless you polish it and dress it down a little with some sand paper or something).
I use Reg Barber tampers, btw. You can order them in any 1/10th mm size.
Again, the best idea is always to measure your actual basket if possible.
BTW, these measurements should apply to the 49 mm Elektra baskets as well. The Elektra baskets will also work on your La Pavoni too. Stefano's sells them (they are an advertiser here). The single shot basket works really well on the La Pavoni, since it allows you to use 8 to 9 grams of coffee, which matches the 30 ml size of one lever pull. They also have a very nice double basket (for the Elektra) that works on the La pavoni and is a little deeper than the normal La Pavoni baskets (and it allows you to hold more like 14 grams of coffee).
Ray
