Get yourself a good 90 degree square. Use it on your grinder face/table and then on your handle and guard. I use a colored liner and use it between the guard and the handle material.... AND I color my epoxy the same color (acrylic) as the liner material so any very small voids are hardly noticeable.
I use the square, 3" to square up drilling pin holes and handle/guards and a 6" for platten and disc sanders. Hope this helps.
I use the square, 3" to square up drilling pin holes and handle/guards and a 6" for platten and disc sanders. Hope this helps.