No it's not rocket science either but, some people think they must match the OEM angle when you sharpen their blades......and if you don't, some get pissy!I just use a free standing grinder with a 10 in. wheel and 2 HP. motor. Hand hold the blade and less than a minute per blade. Don't over think this. It is not a chefs knife.
Actually, I do match that factory angle with the belt sander when the blade is in real good shape, which is NOT often. Most get the angle grinder!WHAT! You don't match the angle perfectly and get them shaving sharp. And you call yourself a mower mechanic. You need to send them "pissy" folks to the $100/hr dealer. I do. Actually had a customer tell me a dealer he bought a mower from tell him they only install new blades and not sharpen them for insurance reasons.
Actually, I do match that factory angle with the belt sander when the blade is in real good shape, which is NOT often. Most get the angle grinder!
New blades for Insurance reasons.....I'll have to tell my boss that one!
And a $100 an hr dealer......no comment!