I have a craftsman circular saw that is approx 15 yrs old. I am unable to tighten the blade or remove to replace with a different blade. there ia a 1/2 inch nut on the outerside but no way to hold the inner washers tight to break the seal. I believe there is some sort of wrench that I should have but don't have. Is there another way to change blade, or order the wrinch? Thankyou