Step 7: Welcome to the DRO
Most modern lathes have a Digital Read-Out fitted to them. This is a lot easier than squinting at the tick-marks on a handwheel.
The two metal lathes at TechShop San Francisco (Jet Model GW-1440 W3 if I recall) both have DROs.
So here's the idea; get a clean surface that is aligned to the lathe (by facing and turning). Now, without moving the tool from the last operation, zero the DRO. Now you know that any number you see on the DRO will be relative to the surface you just cut.
Following facing, you zero the Z axis (that's the spin axis) on the DRO. This means the cutting edge of my tool will display its position relative to the clean end of the piece. Here's the trick; because of backlash on the carriage traverse, you have to do this in a specific way. Starting off the piece, turn the handwheel until you are cutting into the face. Now lock off the carriage using the lock-off lever. Use the cross-feed traverse to make your facing cut then, without touching anything, go to the DRO.
Hit "set zero" and then hit the button next to the Z axis.
You do the exact same thing to set the X axis on the DRO, except that you are working at right angles to the previous operation, and you don't need to lock the cross-feed.
There's another wrinkle to this, but before we do anything else to this piece we need to install the live center.