As has been hinted at before, the “ in true” mounting surface for the burr is not the recessed area but the rim of the burr. It’s the rims that are accurate to a few micron…| measured enough of them. In early testing we realised this and it was changed to a rim mount. Plus the holes in the burrs have “burrs” at the bottom which I had to ream out before using proper accurate “shim washers”, just to facilitate early testing for carrier hight in relation to burr depth.
So sadly, your method is absolutely not the way to shim burrs (not on the duo, or any grinder really)
P.S. When a burr is correctly fitted, that black impeller should have so tiny amount of left/right play, if it doesn’t the location tab isn’t properly in the recess and is being pinched by the burr
The lower burr is an issue only when the sweep arms are above the height of the lowest coffee exit point on the burr, the hole in the little diamonds.
With the top burr you need to check very carefully that the holes around the periphery mentioned above are just above the edge of the burr carrier….If both these points are true, the burr sits high enough in the carrier and no shimming is required. You can upload close up photos if your not sure.
The SSP burrs I have tried, from memory are thicker than the Mazzer ones, but there may be some models that are not?
