Don't forget to sand the blade ends and the blade holders to get rid of blade preservative and finger oil you put on the blade ends handling them Thin spirals don't thumb screw to tight as it will pierce the blade flat to nothing and break when you start up te machine.It's a fine line on tightening for tension and gripping the blades. LOW COST machines are terrible for breaking blades as they are not tweeked for performance,They snatch the blades rather than gently .Just like a high lift cam shaft in a car ,The up and down motion is erratically,strenuous on blades