Baz
This end mill grinder thing comes up and up. Basically, it can follow making up a set of crude collets From SQUARE or rectangular stock with holes drilled in to cover your dimensions of your end mills, slot drills whatever. Being square, it saves the worry about indexing, rotary tables and such that many do not possess. Once you have ONE lip in position, the other or the remaining three automatically are in line.
Basically, you need a double ended grinder with two rests. They can be wood so long as it is smooth.
Both are set at a position where the end mills will be dead on centre with the grinder spindle. The angles are 5 and 15 degrees. It means that the grinding follows doing the primary and secondary cutting edges of your mills. In practice, most mills etc are dulled and only a slight even lick on all edges will get things right.
The foregoing - despite its simplicity- is what one of my tool holders does on my Kennet.- at a vast cost and then time and effort to make it.
Moving on- a bit. This principle is why I have little time for belt sanders which I know you like. With a grooved/slotted bit of square bar and the odd grub screw, you can do lathe tools as well.
Following the same bit of metal with a hole in it, putting longer rods in on a mini mill with grub screws or wing nuts is one way of adding stops. True, you can put a clock gauge on, you can make turrets which rotate or even play with tilted dividing heads, collets and such wonders but a bit of square and a hole and grub screw will do most things.
For the record. Two old fellows saw all this simplicity and how it would be lost. We set off to get it on the net- using articles which had appeared variously in magazines like Model Engineer. Other old and often dead engineers had left them as their contribution to our hobby. And then we ran into 'copy right' issues.
I scrapped my stuff and assumed that Jim Early in the USA had done likewise. Jim is no longer with us and then an e-mail arrived with the sad news. It also said 'we have a lot of the articles which were not destroyed'.
Perhaps it may explain a lot of things. Certainly, I am not going to 'do' photographs- even if I had a digital camera.
You'll have to with the 'words'- sorry!