A busy day today, assembling, and playing with the grinder. It went together pretty much as expected, but once the bearing and spindle were fitted, I found that I had to machine a little bit off the PEEK fingers, as they were fouling the cap. I'm happy with the bearings, once the adjusting nut was nipped up, they were butter smooth with no play. I checked the burr runout with a dial indicator, and it is a shade over one thou'.
I had no idea what size I needed to grind, so used some masking tape and feeler gauges to set up an initial scale of 0.1, 0.2, and 0.3 mm, and ran a few shots through the Rancilio Audrey. 0.2mm was super fine and an absolute choker, 0.3mm was a bit gushy, 0.27mm was in the ballpark, and 0.25mm was on the money for an 18 gram double-shot. (I'm surprised how small the range is for an espresso.)
At 0.2mm the grounds were uniform, but a little clumpy. At 0.25mm, they were nice and fluffy with no clumping, and made a nice pyramid. Static was a problem when I was grinding into a plastic container, but by the afternoon I was using a metal cap, and it wasn't too bad. It may have been the container, or perhaps a change in humidity?
At this stage I'm still using 'expendable' Aldi dark roast beans to get a feel for the grinder, but tomorrow morning I will run some of my favourite beans through it and see if there is any difference between Rocky and this grinder. My neighbour is a bit of a coffee zealot and has a you-beaut E61 type coffee machine. I should give the grinder to him to try, and get a more professional opinion on it. Here's the first coffee made with the new grinder.
Still a few things to do - I need to make a base, a cap for the top of the chute, and a cover for the feed funnel to stop it spitting beans out. I will make a quick wooden base, but now I've seen how nice the anodising looks, I feel that the grinder needs something better. In the longer term I may get a local company which specialises in making items from sheet stainless steel to knock up a nice brushed cover for the motor and gearbox. Or maybe something clad in embossed black leather, , , kinky!
PS. It's funny, but when using the Rancilio Rocky grinder, I've never given much thought to particle size - just ground the beans and made the coffee. Today I thought about the 0.25mm burr gap and wondered what the actual size of the resultant coffee particles were. I did see somewhere where a guy ran some ground coffee through a set of laboratory screens, and worked out the range and percentage of particle sizes. Hmmm, don't overthink it Steve, just make the coffee.