....how _do_ I set one up on the mill, so I know exactly where the centre of the rotab is in relation to the spindle centre?
I have at my disposal: A regular DTI, a finger type DTI, and a small quantity of patience...
basically, I'd like to know when I'm plumb above the middle of the rotab with the cutter, so when I offset by X, I know i'm now cutting a circle with radius X (assuming the work is also centred on the rotary table).
However, this leads to my next question, along similar lines; I need to cut a curved section out of a piece of work (see the attached "metallic 3D" Crap-o-Cad). I don't (yet) know the radius but I'm hoping it'll fit on the rotary table, let's assume it's 8" & my rotab is 12". What's the easiest way of setting the block up so that it'll cut the desired 8" radius? I'm thinking, once I've got the rotab centered, dial 8" of X-axis offset, and with a centre point tool, locate the block square on the table with the pointer pointing at the line, then simply fettling until it follows the right course. However, whilst that should certainly work for my purposes, it doesn't seem like a terribly accurate way of doing things; Surely there must be a better (more accurate) way?