Táriba The nibbling process cuts a contour by producing a series of overLapping slits or notches. This allows for complex shapes to be formed in sheet metal up to 6 mm (0.25 in) thick using simple tools. Nibbling can occur on the exterior or interior of the material, however interior cuts require a hole to insert the tool.
http://karen-keogh.co.uk/portfolio/sigirya-ii/ The process is often used on parts that do not have quantities that can justify a dedicated Blanking Die. The edge smoothness is determined by the shape of the cutting Die and the amount the cuts overlap; naturally the more the cuts overlap the cleaner the edge. For added accuracy and smoothness most shapes created by nibbling undergo filing or grinding processes after completion.