I have used a lot of files too,
and I don't find Nicholson files better then say Oberg, Sandvik, Facom, Valor....
They are a good grade of files, but since Nicholson makes a lot of series of files, they've been known to make crap too.
I currently use Sandvik files, and they are more consistent then Nicholson files in quality.
-Grind the teeth off before you use them, this can be done rough with an angle grinder.
-Anneal by letting them cool down slowly. I do this in a big crucible filled with very pure charcoal ashes. Leaves the blades too hot to touch even after 24 hours. If you need to really soft anneal, put a piece of hot metal by it and let it soak for a few days. I have a bar off HSS which I always use for that.
-Always oilquench, as you don't know what steel you are working with. Check hardness, and if it is not fileable, you're dealing with good steel which needs a temper.
If it is fileable, check if the lower layers of steel are fileable too, if they are, this is low carbon stuff and not suitable for knives.
greetz, Bart.
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