Thanks Rick,
I do not think an angle grinder can ever be a precision tool but a guide is an aid to manipulation in use. I did think of providing two support pillars but that brings assy problems, I did ream the thro hole to 8mm and is a reasonable fit.
If greater accuracy is desired I have used a simple system like this in the past which is adjustable for play.
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BTW that grinder is brand new and will stay with the fence (I hate disc swapping) I now have 4 grinders.
Regards