In coffee processing, dry milling (or parchment milling) follows wet milling (the collective steps from coffee cherry to dried parchment). Dry milling is when the parchment skin, the husk, and the silver skin are removed from the bean. The result is green coffee, and the beans are graded.
Our coffee is dry milled at the Holualoa Kona Coffee mill, who mills for many farms.
The mill office. The milling starts in that open area beyond the chair. 
Dried parchment is emptied in the grate at his feet. It’s transported up the elevator to the huller which removes the parchment husk. 
Green beans emerge after hulling and go up the elevator to the right to the grader.
This video shows the parchment going up the elevator towards the huller.
On the right is the elevator which brings up the green beans, which then go through the grader. The result is each tray contains a specific grade: peaberry, extra fancy, fancy, number one, prime, triple X, and rubbish.
Each tray contains a specific grade. The middle tray contains extra fancy. The closest, fullest tray contains fancy. Other grades are lower & some aren’t visible. 
This area comes after the trays. The levers control which grades continue down to the gravity table.
The green coffee comes from the grader above, down to the gravity table. The heavier, better quality beans stay on the higher left side; the lighter, lower quality beans are on the right side. The master miller Jason knows where to adjust the two boards that control which beans go in which of the three bins.
Occasionally Jason re-runs a bin. A master knows. 
The green beans from the top quality bin. 
The beans from the inferior quality bin.