Hi Dave,
If you have a standard toolpost (a simple block with slots for tools in all four sides) then the ideal would be tools with shanks of such a size that the business end falls dead on centre height. You are unlikely to find those, and resharpening will alter the height of the sharp end anyway. So you need to get tools smaller than the ideal, and assemble a collection of shims of varying thickness to use as packing beneath them. To save fiddling about each time you change a tool, get some small containers in which you can store each tool and the shims which get it to the right height, though HSS tools ground to shape at each end complicate this.
I'm not familiar with Myfords, but 5/8" sounds a bit on the big side for a lathe of (?) 3.5" centre height.
If you do go in for grinding your own tools, bear in mind that smaller sizes of blank like 1/4" or 6mm square need a lot less grinding. Though there is some loss of rigidity, this is usually of no real consequence if overhang is kept to a minimum. My lathe will take 3/8" or 10mm tools, but I use 6mm much of the time.
Andy
