With the caution that the stuff you need to get expensive knives all the way up to really, seriously sharp will cost more than $30, this is a standard tool with good reviews: http://www.amazon.com/DMT-FWFC-Double-Diafold-Sharpener/dp/B00004WFTW/ref=sr_1_11?ie=UTF8&qid=1417711102&sr=8-11&keywords=diamond+hone