i bought a sharpener a few years ago- oh boy is it ever dangerous! you think the blades themselves are dangerous---then try to use this (tool- and i use the term loosely) and find out just what danger is!
you have to handle the blade- get it on this (spindle) put this *thing* together- turn it a few times----then you have to take it apart and struggle to get the blade back out without loosing any digits...after a few tries we decided it did not make enough difference- keep a sharp edge long enough to justify the danger involved- and put it away somewhere- now i watch for sales & coupons- and always have new blades on my Christmas/birthday wish list- hubby is great about buying me a couple 5packs of new blades for my stocking every year :)