ds wrote:0.010 µm is 0.00001mm which is a ridiculous tolerance that very, very few in the world would possibly be able to achieve let alone measure. Aerospace/high precision tolerances are at and below say +/- 0.007 mm and even that is too much for a grinder.

I don't agree often with you, but in this case I do.
Denis got some numbers wrong.

ds wrote:I height doubt claimed tolerance of less than 0.009mm on flatness. How is that measured and with what kind of instruments? Run-out maybe, flatness over 4" area, I doubt it.

You can only measure it on a lathe machine, but there you can get it better than 0,01mm
This one was measured before getting it revised.

http://www.youtube.com/watch?v=lPuD3Otxn5c

ds wrote:You can't put Bugatti Veyron tires on Yugo and go over 250 mph with it...

Yes you can, but you cannot go over 250 mph with a Bugatti when the engine inside is from a Yugo

Terranova wrote: You can only measure it on a lathe machine, but there you can get it better than 0,01mm

Which is exactly my point. You are not going to run that part in lathe and grind coffee on a lathe.

ds wrote: You are not going to run that part in lathe and grind coffee on a lathe.

This doesn't make sense to me, or I just don't get it.
The more accurate all parts, the less tolerances where all the tolerances meet - at the burrs.
So it is totally OK to have all parts as accurate as possible.

If there is a lets say 0,03mm run out at the shaft, it doesn't mean that all other parts can also have a 0,03mm run out because at the burrs it is an addition of all parts which makes it much worse than 0,03mm.

I fked up the measure unit.

The gauge I measure with it's 0.01mm and doesn't move when I get the grinder aligned. This means it has unde 10 microns play. This is enough for me.