Thats it mermod
...another name for a catch plate is a face plate
1. think of a piece of black bar
rough peeled surface & oversize on diameter
2. center both ends of the bar
3. install the face plate to the headstock + install the fixed center to the headstock
3. install a live center [if available] to the tailstock
4. install the length of black bar between centers
5. secure the drive dog around the bar in the dead center in the headstock & align the right angled finger of the drive dog in a convenient hole or slot in the face plate * BINGO
In theory you can now machine the diameter of the black bar..........remove from the lathe for whatever reason..........return it to the lathe & becauset it is returned to 'between centers' the accuracy is only governed by the accuracy of the headstock bearings......
You also have the advantage of machining the full length of the bar stock between centers without end for ending in a chucked condition which means the dial indicator setup each time for ZERO runout
Mind you..... it has been many years since my mechanical apprenticeship
...but some things never really change ..........
......Derek