This is one of the crusher type, rather than a spinning knife.
It failed to get appropriate maintenance last autumn unfortunately - ie one of us used it and didn't clean it out. Nor in hindsight did I pour some oil over the grinder wheel which would have been a good idea.
I've got the casing off and it's obviously the crusher grinder wheel where the problem is as I can move the motor fan 20 degrees or so quite freely, but the wheel is solid. There's an adjustable plate for the grinding and that's free ('ish!).
Any bright suggestions? There are 4 bolts holding on a plate carrying the grinder end bearing - releasing them has achieved nothing.