Fred,
Normally, when grinding on the lathe, the chuck speed is very low, plus you are taking super fine cuts. So unless you do something very silly there is very little chance of your chuck unscrewing.
There are basic rules for direction of chuck and stone relationship when grinding internal and external surfaces, but because I am not highly skilled in the job, I tend to try the correct direction first (surface and stone running against each other) and if it doesn't give me the finish I want, I will experiment with other directions to end up with what I want. Wrong I know, but sometimes needs must.
This post just might help a little
http://madmodder.net/index.php?topic=553.0One thing to take note of, dressing the stone is of paramount importance, you can't usually do much about the balance. I made my own dressing unit out of an old mag base and a single diamond dressing stick. If you want a pic, let me know.
I tend to use more mounted points rather than wheels (of course, you have to have the collet chuck to do it), and for external I generally use a 1" disk type mounted point if it will do the job. But sometimes I just can't get in and have to use the 2.5" wheel instead.
My TP grinder is normally used for truing things up to give a nice surface finish coupled with very accurate sizing, but where it really comes into its own for me, is grinding tapers for air or steam control. I get no tooling marks left on the very small surface areas, so I never have problems of leaking valves.
John
