If you ground off 1/4" off the front sight you will have no front sight left. The highest point of a J frame front sight is maybe a little less, or just about 1/4" high.

When you take a little bit of steel off of a front sight you are talking about 1/64" or 1/32" not a quarter inch!

Which brings to mind if you do take a little bit of steel off of a front sight you wouldn't use a bench grinder! You would use a fine file.

At least you asked some questions before you acted. Everyone had to learn at the beginning, and nobody knows everything. Asking questions is the smart thing to do.