Phil Trueman posted a query on the Centroid forum about rear mounted tooling. His machine is very similar to mine in having a turret that requires CCW spindle direction for external tools. That got me thinking, as I had no idea how this is handled, yet it's something I'll need to bottom out myself sooner than later.
The turret in my machine presents the external tools from the rear (ie X coordinates are negative) and expects the spindle to rotate CCW when machining. Internal tools such as boring bars move in positive X coordinates ie they operate "in front of" the spindle with CW spindle direction. Not all turrets are like this - it depends if the tool is "upside down" in the turret. In my case, external tools are mounted "the right way up" like this:
If the tools were mounted "upside down", the spindle would turn CW. The reason for NOT going this route is that the cutting forces would tend to lift the turret / cross slide / carriage. Some machines are designed for CW spindle of course - but not this one.
One downside of this scheme is that the tool tip needs to be presented 3/4" above the turret face. That's 19mm, so a standard 20mm toolholder will present the tip 1mm above centre height. Sure enough, when I measure the height of the toolholders that came with it, they have metric 20x20 shanks that have been ground down to 19mm height. Something to bear in mind when I come to fitting tools to the turret.
The other slight downside is that the "handing" of the toolholders is flipped by moving them behind the spindle. So the default tool for RH turning in this scheme is actually a conventional LH part.
I managed to get the tool set up correctly and the spindle direction set to CCW within the tool library definition for the threading tool (as used in my first thrading trial). But no matter what I tried, I couldn't get the tool to reside on the -X side of the spindle. Note the X axis direction shown here - flipping it within the operation setup options doesn't help, as it gets realigned when you regenerate the toolpath. Hmmm.