I am not a professional by any stretch of the imagination but, I have thrown a lot of sparks over the years. I have a cheap 2"X48" belt grinder that I have modified a bit trying to get just what you are looking for. Make sure your platen is flat, and your belt is moderately tight against it. Next? practice,practice, and more practice. I know that sounds trite but, it's the truth.
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A Paladin in Hell!