Instead of of grinder/grinding wheel to remove the material to make the safe edge,,do it on a belt grinder.
A grinding wheel & free-hand operation usually results in an uneven surface as there's no backer (platten) and most shop grinding wheels are less than perfectly flat anyway with grooves and ridges in them.
Even a hand held belt sander mounter upside down in the bench vise and switched on makes a usable belt grinder for such tasks. Even they have a sheet metal platten on the bottom or you can use the end roller to grind off of.
As with any grinder/sander,,,Careful with orientation of belt drive direction and which way you're holding the piece being worked on.
With a fairly rough grit belt (150/180,,) it'll remove material quickly without heating up the piece real fast.
It cuts nice and smooth as you drag it back accross the supported belt. Do it with the right amt of pressure and speed with each stroke, and you don't even heat the work piece up enough to worry about dunking it in water.,,but it's a good idea to keep a water can handy anyway!
Once the major work is done,,switch to a fine cut belt if you want to give the surface a nicer finish. A couple of swipes will do it.
Cut the safe edge of the tri-square file down far enough to give yourself a real sharp corner edge on each side. That'll cut a sharp edged dovetail w/no blunt corner.
