I was browsing youtube some weeks ago and came across the video posted below about a simple tool that can be used to indicate parts quickly on the lathe. Still very much learning and trying to find my feet in model engineering, I often remove parts from the chuck only realising they needed to stay in the for next job or understanding that if I had planned a little better, the job could have stayed in the chuck for multiple steps.

The tool is very simply a bearing mounted on some sort of arbour. In my case it is a piece of steel bar
and the bearing bolted to the end. The chap in the video has welded the bearing in place and this is actually better. The problem I have with my bolting method is that the bolt pertrudes and can interfere with what your trying to true up in the chuck. That said, it hasn`t been a problem yet but can see that I`ll get in a situation where I can`t use it because of the nut at some point.

The tool is setup on the tool post so that the bearing is held parallel to the jaws. The work is lightly clamped in the jaws and the bearing moved towards the work piece until the bearing spinds consistantly.

The video shows much better than I can explain but I have to say that this has been working 100% for me and has made this job much quicker.