I want to buy a spokeshave for making curved edges on boards and have seen this ad for a cheap stanley on axminster "Made from fine grey iron with epoxy black finish. The 54mm(2.1/8") cutter has full lateral and vertical adjustment. Available with either flat or round base for convex or concave work. " Do I need to buy both models or which is better for most purposes ? Is the flat base one for rounding edges ? Any info appreciated cheers.