You need an "all of the above" choice for your poll.![Big Grin](/forum/images/smilies/biggrin.png)
When I am doing a one-off setup I will probably touch off directly to the O.D. of the part with all tools.
If there are several parts with the same O.D. I will probably do the same thing.
When I will be doing parts with different O.D.s using the same set of tools I will either touch off directly to the largest part. Or I will touch off to a reference point that is higher above the table than the O.D. of the largest part. Then when I do the different parts I will enter a Z value into the Work Zero that is the distance from the reference point (or largest O.D) down to the O.D. I am working on. Actually if they are repeat jobs this value will be entered from the program using a G10 command or a G52 command. The Z value(s) are all negative
I neverset the Z tool offset to the centerline of the 4th axis. The reason for this is that then the Z value entered into the Work Zero has to be a positive value. If a negative value is accidentally entered the result is the tool tries to go below the centerline which probably creates a bit of havoc.
When the value that should be entered is negative and a positive value is accidentally entered the tool stays well above the work and just machines air. This creates far less havoc.
An open mind is a virtue...so long as all the common sense has not leaked out.