I just maintained, cleaned and re-set up all my tooling for my Mach 4 Mori Seiki SL-1 Lathe and I was wondering why the lathe screen can't use Touch. I mean wouldn't that be a hell of a lot easier to setup tooling.

Take a 1" piece of stock > cut face set T0101 Z Fixture > Cut some off the diameter > Measure > input into Tool Table. Then switch to a new tool and use Touch to set those same dimensions into the tool table.

Works on mach3

I don't even see on the lathe screen in mach 4 where it would be.

It is not on the lathe screen.  You can open a mill screen and export the "touch" section of the screen and then import it into the lathe screen. 
You might have to get on the back end a little bit to make it work properly. 

Hmmm ok. How accurate do you think that will be? I have been machining for most of my life and my theory is that unlike milling tools lathe tools bite in a bit more so just touching off might not be that accurate?

That depends on how rigid your machine is.
If you set this up to touch off tools and when you make your finish passes on your parts and you notice that you initially always have to take x.*********x more; then just make the button to set the tool fudge the tool offset by that amount from the beginning.  Then you can just adjust as needed with wear offsets or something.

Cool. I haven't messed with mach 4 in a long while, can you link me to somewhere to explain how I would bring over the touch tool setting from the mill screen?

I’m not sure if anyone has explained how to do it. I’ve only done it a couple of times.
But in the screen editor, you have the design tree in the left that contains all the tabs, pages, buttons, etc…. Find the touch off tab and right click it and you can export it. Then you can import it into the lath screen.
Something like that.
Make a backup of your original lathe screen set in case you mess up. That’s one thing I dislike about editing screens. There is no undo button. If you screw up… start over. Then make a change, close the editor, save that screen set as a copy and make more changes.  Play it safe.

Cool. Thanks.