Hey Ken,
You will find your vice super handy for tons of things. Nothing like having a third arm sometimes.
Here are some other good things to know when you tackle sharpening a lawn mower blade. I learned at least one of them the hard way so I thought I would share.
If you are just honing the fine edge, I personally think a large hand file is a better tool. It's easier to not change the correct angle and easier to keep things in balance. If you can hand file it twice a season or at least every season, you may never need to go back to the extra steel stealing of a grinder. It doesn't actually take much longer either if you have a good file. It's really amazing what a good file can do.
Angle. Be careful to keep the same angle when using a grinder. It's easy to change the angle when you can take off so much steel so quickly. My push and tractor are 40 and 45 degrees respectively. A flatter angle might seem better but it will chip easier. Also, remember your grinding disk is round. You need to keep things even or the roundness will give you too thin an edge which may be sharper but is more prone to chipping.
Balance. The other easy thing to do with a grinder is to remove a bit more on one side or the other. If the blade is not balanced, you will get bad vibrations. I know, I've done it.
Heat. Don't press down hard with the grinder or use it too long without giving the metal time to cool. If you heat the metal too much, it will lose it's temper and will chip and wear faster. If it changes colour, you created too much heat.
