CNC Information | Learn CNC | CNC Programming G-Code

Hello I need help understanding how the tool offset works on a surface grinder.
I am programing a chevalier smart 818 profile grinder (3 axis) where Z axis moves the table(wheel) in/out-that is toward/away from operator, Y axis is up/down and X axis is left/right.
1st question- is this standard axis ID for a surface grinder? why is "Y" up/down?
Second, and my main concern - I cannot get my head around the tool offset theory - I am typically using an 8" diameter wheel but the widths will vary depending on the work to be done- the radius will also be different -some wheels maybe full rad some sharp corner some are in between. What determines the offset here. I am looking at this from a standard 3 axis cnc mill perspective and trying to see the wheel as a emill sharp,bull nose or ball and am very confused!! Any help/comments or ideas where to go to get the info. is appreciated. I would like to use Bobcad to generate my g code for this machine as well. Thanks, rj

Been a while since i ran cnc grinders. As your wheel widths you should have some kind of variable to set your beginning width, dia, etc. Then once you do your first dress the machine will comp. for wheel wear and dressing.