FWIW Dept, Years ago at a Blacksmith Convention we had a gentleman in who explained about files. Years ago files were what they classified as 101 points of hardness, which I assume means 1.01% Carbon content. This is extremely hard as Bearing races are 1.% carbon. Mondern files at that time were .95% of 95 points classification. At the time you could still get 101 point files, they were called industrial quality files. Don't throw your old good Nicholson files away, Resharpen them, which has been discussed on Sawmill Creek before. It used to be that the best Drill bits and Files that were Black Oxide finished were the best.

File usage is also a determining factor on how long they will last. Back in the day a good portion of a Blacksmiths time was spent filing and finishing things that he had forged. During my apprenticeship I was given a piece of 1 inch shafting and 2 files, one being a Bastard cut and the other a mill cut. These were the only two files I was allowed to use and I had to using only the files, form 1" long sections on the shaft, 1/4" round, 1/4" square, 3/8" round, 3/8" square and so on. I was repeatedly informed that drawing the files backward while resting on the material would dull them. Took me I think 3 days, and I was never so tired of filing, and my arms felt like they were gonna fall off. Years ago they made a handled file that had one safe edge that were made for filing the drags on Chainsaw Chain, which is really hard. There was an older gentleman that came around with a pickup full of used drill bits, files and milling cutters etc. He showed me how hard the handled files that were actually new were and I bought a dozen or so, I still have several of them and I never did wear one out.