I've been in discussion with Hansung and asked him about the performance of the 58mm burrs vs the oem Italmill / Mazzer burrs.
Reply as follows:
It is faster , and can make uniform grinding result than original one.
Also we tried to solve torque problem as it happened with 64mm burr set due to aggressive geometry. (caused by small motor)
Our 58mm burr set does not have the highly aggressive geometry because of small size and small motor. I am happy with espresso from 58mm now, enjoying it.
Faster would solve the only issue vs my previous 64mm burr grinder. Outside of some little quirks, the F4 E shoots well above it's 58mm burr size in the grind quality and better yet in the cup. Currently takes 15 seconds for a fine espresso 18-19 gram grind. I understand that we're talking about seconds more and not minutes, but that's 40% more seconds than my previous E37 64mm grinder. I'm sure the hand grinder crowd are raising their eyebrows regarding seconds to grind. Less time to grind means less noise a good thing when you're the first one up in the morning. I mostly make 2 double espresso shots per session.
Percentage difference of 9.83607% from 58mm to 64mm. F4 E and S.J. burrs operate at same speeds 1400 r.p.m. (50 Hz)1600 r.p.m. (60 Hz).
Non coated Products : 1,000 kg - 2,000 kg
Coated Products : 4,000 kg - 5,000 kg