I didn't think there was any difference between a grinder, or mincer. I though that 'grinder' was just what people in the US call our (UK) mincers?
They have 'ground' meat - we have 'mince' meat. But they're both the same thing.
Mincers tend to have at least two sizes of cutting disks. A larger holed one for course mincing, and a smaller holed for a finer mince. Even maual 'mincers'

have at least two disks, and can be bought new for under ÂŁ20. First putting the meat/bone through the course disk, and then re-doing it with the fine disk, should get the bones nice and small
