I did open it here Breville 860 Grinder Teardown
It surprise to me when you have a swift respond! And how shame at me when I can not find it in the text! :-)
After reading I fig out this could be done, hope will success with my limited skill!
I am going to order the 3D Impeller
I have Breville 860 espresso machine and I having problem: the coffee grind pour coffee out too slow, it look loke jam some where. May I use this one to improve the situation?
And BTW, in my machine, I do not see the nut, how can I open the lower burr?