Yes, side ax and broad ax are two names for the same thing -- an ax or hatchet ground on one side, like a chisel. I believe that side ax is a more British term while broad ax is preferred in American English. Salaman also illustrates a "wheelwright's ax which is sharpened in this manner. For some reason, American English uses side ax for the cooper's tool, but broad ax for the larger tool used for hewing beams.