I absolutely love Oberg cut files! Halfway between a float and a file, they cut aggressively, wear slowly and leave an exceptionally smooth finish. They can be used on metals, but I tend to reserve mine just for wood.
Carl Oscar Oberg founded C.O. Oberg & Co in 1850. The company was eventually taken over by Bahco, hence you will see the brand 'Oberg' on lots of Bahco files.
'Oberg cut' files are a separate thing, a specific toothing pattern that was developed by C.O Oberg & Co with waves of interrupted single cut teeth. They work in a similar way to a toothed plane iron, restricting the maximum size of shaving to control the forces transmitted to the underlying material.
Because the teeth are offset in waves, the next one planes the bit that the previous one missed - hence the beautiful finish.
I use an 8 inch (200mm) for most work, but for larger surfaces the more powerful 10 inch version gives a longer stroke and faster material removal - still with a lovely finish.
For best results, hold the file at both ends and at a slight angle to the work. Advance the file forward and across, with even pressure to bring the maximum number of teeth into contact with the work. Avoid rocking and lift off on the return stroke to avoid dulling the cutting ridges.
To clean your files gently brush out any accumulated debris with a soft wire brush or file card, always going along the ridges rather than across them. To minimise the chances of the file clogging when working with soft metals, apply chalk liberally to the surfaces before you begin.
Bahco product code 1-106-10-1-0