M42 Bi-Metal Hole saws take the form of a short open cylinder with saw-teeth on the open edge, used for making relatively large holes in thin metal.
Adjustable Arbor For Hole Saw
3/8" hex shank,with 5/8" -18UNF thread.
fitting hole saw diameter 1-1/4" to 8-17/64" (32mm to 210mm)