It took me a while to justify the cost but in the end I can honestly say they are worth it. The Stewmac gauged nut files are the business and give wonderful clean nut slots. If you are a bit 'ham fisted' the thinner ones are prone to breakage yet all will last a very long time if treated with respect.. At a little over $10 for each size a reasonably useful guitar set is within grasp.

http://www.stewmac.com/Luthier_Tools...ic_Guitar.html

It is worth noting that their "double edged nut file set" will do both guitar and bass....

Only real complaint is the slow freight. My last order from Stewmac took 6 weeks to get to me in regional Queensland.