Why Is This Tool Important


One of the issues that comes up among technicians is how to align coffee mills.
Mills are scerewed onto a plate that is secured to a shaft that rides on bearings that are mounted to a cast chassis and all of these components have to line up perfectly parallel to another mill that is mounted to a carrier suspend on springs or threaded into a chassis . . . and everything has to be perfect.  Including the mills themselves.
We mark mills with sharpies and rotate them in hope of an even wear pattern because any variation in the distance between the mills results in a variation of coffee particle size.


A Fix for Problem We Knew We Had . . . and One We Didn't


SInce the flat surface of the mill doesn't actually do any of the cutting, it seemed a good solution was to find a way to knock down any of the high spots on the mill.  Using each mill to slightly remove any material from the other would gaurentee that the mills were perfectly flat and more importantly, mated and parallel to each other. SInce the edge of the cutting surface wasn't going to be affected, we wouldn't be shortening the actual life of the mill.  
Just to be sure, we put the mills under a microscope . . . and found something we didn't expect.
The first thing we saw was that the surface of the mill wasn't very smooth.  The rough finish of the mill, while not that apparent from a distance, appeared to work like sand paper against the ground coffee particles.  The result had to be excess heat and excess fines.
The second thing we saw was that because the circular cutting surface was ground in a linear direction, each tooth was sharpened in a different direction.  Some teeth were sharpened along the cutting surface while others were cut away from the edge.  Small bits of metal adhered to the edges of many of the teeth and the overall edge quality was really inconsistent.


By using two levels of micron abrasive disks, not only could we remove the grain from the flat surfaces of the mill, leaving a near mirror finish, but we could ensure that the honing disk would refine the edge of each tooth and a near perfect 90 degree angle.  This virtually eliminated the burrs present in the conventional surfacing process and yielded a much more consistent, razor sharp cutting edge.


Because the mill rotates at as much at 1400 RPM, it was necessary to insure that the honing disk was perfectly centered on the mill.  The tool that we invented does just that.  It also aligned the mill with the centers of the retention screws so that not only are the mills parallel when finished, they are perfectly aligned to each other.


The honing disks use a pressure sensative adhesive backing from 3M.  The initial honing disk of 30 microns removes surface imperfections and sets the geometry of the mills while the second disk polishes the final finish at 12 microns.