Abra File Saw: Sometimes called a tension file. Consists of a thin, round file about 3 mm in diameter which can be fixed into a frame. As the file has teeth all round, it may be used for cutting in any direction. It is very useful for cutting curved shapes in sheet metal.
From
by P. F. Lye - 1974 - 72 pages
http://books.Google.com/books?id=yFccw_x4h5MC&pg=PA66&lpg=PA66&dq=%22as+the+file+has+teeth+all+round%22&source=bl&ots=VOtj6xxf1Y&sig=DcdiD99pQ5DqN92mEVsG3VWlnjk&hl=en&sa=X&oi=book_result&resnum=1&ct=result
Abrafile is claimed to file any material.
Be careful and don't touch the thin file
This file is in the form of a piece of hardened wire with teeth in it. Along with two clip-holders it replaces a hacksaw blade in the hacksaw frame and can be used to cut a channel in any direction about 2-3 mm wide. Correct tension prevents it snapping.