Guide updated on 18th April 2019 to recommend the Bahco file.
Guide updated on 14th October 2019 to remove the recommendation for a four-in-hand farrier's rasp as this is not hardened.
Guide updated on 11th November to recommend a bastard cut file too.
A 12” (305mm) file is usually the longest length used in woodworking and metalworking, Paul recommends using a 10” (255mm) or 12” (305mm) flat file ideally with second cut (medium) teeth, but a bastard cut file will work well too. The difference is simply the size of the teeth. We purchased this Bahco 10” file from Amazon, it costs £22.25* and Paul uses it daily. He would recommend this as a first choice. This is also available on amazon.com
*Price correct as of December 2019