Abstract: The invention provides a method and apparatus for spirally winding a magnetic core from at least one filament of magnetic material. Two congruent mandrel plates are mated together in facing relation to delimit a mandrel having an outer peripheral edge portion. An annular channel is formed in the edge portion to delimit at least one channel region having a preselected characteristic width dimension, and a plurality of graduated templates are optionally disposed about the mandrel edge portion to delimit at least one template region having a preselected characteristic width dimension. Filamentary magnetic material is then wound about the mandrel to fill the channel regions and any template regions, thereby producing the core.