Sorry about that Darren, but when I log on, I just go to unread posts and it bypasses all the main headings and it came over as it was something you were doing.
In fact it was the instability issues of such a large lump being carried on a lashed up toolpost that had me worried. It would only take one jolt and due to vibration, that stone would be bouncing around trying to take a 50 thou cut in one go with dire consequences.
John S had a similar setup shown on his old pics about machining a piston, but if you look at his setup, it is mounted rigidly onto the cross slide, and so is deemed safe to operate. You can't see the mounting of mine very well, it replaces the whole toolpost, and is very rigid, and I only use a max wheel size of 2.5" x 1/4" wide, not 6" x 1/2" wide.
I am no super expert on grinding because I don't do it for a living, but I have done many hundreds of hours both surface and toolpost grinding in a prototyping environment. Because of that, I had to attend, every two years, specialist grinding seminars, lasting for nearly a week each time. That was all because part of my job was to mount and dismount stones on on a range of different types of grinders.
If you had to attend such a seminar, people would soon realise that when we are sticking any old grinding crap together, we could be taking our own lives in our hands. Hence the red rag to a bull episode and my warnings about grinding.
With reference to your die grinder, fine, but keep an eye on stone speeds, mine is limited on my toolpost grinder to 18,000 max, well within the normal allowable speed range for mounted points. A die grinder just might be able to exceed the speed limits of certain stones, especially external grinding wheels. People seem to think that just because they can buy the equipment and stones, they are safe to use. Far from it, manufacturers will sell you anything if it gets their profits up, they are not worried if you hurt yourself by using it improperly. I paid less than 10 pounds for my air die grinder, but before I put a stone anywhere near it, I will make sure I have all the facts first.
For other people who use clone mini drills that only have plain bearing supports for the collet, they are asking for trouble. A stone has to be presented to the work in a very rigid manner, and maintained that way during the whole course of grinding. It only takes a minor slip up and that stone will dig in and be liable to shatter at the speed of light if it isn't supported rigidly enough.
Dressing is another major issue. Stones are moulded, and as such are unstable to be used until properly dressed and trued, plus in the case of most surface grinding, balanced as well.
So along comes a totally oblivious model engineer, most probably running the stone way over it's safe operating speed, wobbling all over the place because of being both unbalanced and not dressed and trued up, getting crappy results all because he doesn't know what he is doing, and decides to 'give it a bit more' and hope it cleans the job up. A sure recipe for disaster. Stone shaped hole in the middle of forehead.
Before anyone pipes in that it is not that dangerous, and it will never happen to them, I suggest that you book into a grinding seminar, and they will show you pictures of people who thought they were 'above the law'.
I am not pointing a finger at anyone over this issue, because we all know better, don't we?
Let's be careful out there.
John