Adjustable Blade Reamers
With their broad adjustment range, they are very versatile and economical for repair or prototype jobs, especially when the hole size is determined at the time of assembly. They are not intended for high production work.
Size adjustment: the blades are held in tapered slots by an adjusting nut on either end. To adjust, loosen one nut and tighten the other, moving the blades up or down the slot as needed. Do not over tighten... the slots and threads are easily damaged. To measure size, adjust to a known size bushing or ring, or measure across two opposite blades with a micrometer