[QUOTE=ductape;252081]One of the rare angle grinder modifications that doesn't look like an eventual trip to a hospital. It's a good one!
The only change I would suggest is to rotate the handle 180 degrees in order to have a better view of the rake.[/QUOTE

Yes, I had wondered about guidance at the 'prototype' stage of the build, but found that in practice the centre-line of the angle-grinder gearbox is sufficiently accurate an indicator to place the rake above the joint as it is 8mm diameter and most of the joints exceed that.
It was also easier on occasion to control it by pulling, rather than pushing, the rake especially when encountering a section of hard cement.
Despite any shortcomings of such an amateur tool, the benefit to my non-aching back and knees is very welcome, but when the dry weather returns it remains to be seen how I fare with re-cementing the joints on all fours!