An apparatus for winding filamentary material, comprising: a mandrel rotatable about a spindle axis of rotation and a traverse reciprocating at a distance with respect to said spindle axis to wind said filamentary material in a figure-eight coil configuration with a payout hole extending radially from the inner to the outer wind of said coil; a measurement device for measuring the diameter of said coil as it is being wound around said mandrel, said measurement device including a diameter determination unit for determining the diameter of the coil; and a controller for controlling the reciprocating movement of said traverse with respect to the rotation of said mandrel based on the measured diameter of said coil to wind said filamentary material on said mandrel in said coil of a figure-eight configuration to form said radial payout hole having a constant diameter, characterised in that said measurement device includes: a first sensor configured to measure a length of filamentary material wound about said mandrel, wherein said first sensor includes an encoder configured to generate a series of pulses corresponding to the length of filamentary material wound about said mandrel; and a second sensor configured to measure an angular displacement of said mandrel during the winding of the length of filamentary material about said mandrel, wherein said second sensor includes an encoder configured to generate a series of pulses corresponding to the angular displacement of said mandrel, wherein the diameter determination unit is configured to determine the diameter of the coil based on the quantity of pulses generated by said second sensor between two consecutive pulses generated by said first sensor. a mandrel rotatable about a spindle axis of rotation and a traverse reciprocating at a distance with respect to said spindle axis to wind said filamentary material in a figure-eight coil configuration with a payout hole extending radially from the inner to the outer wind of said coil; a measurement device for measuring the diameter of said coil as it is being wound around said mandrel, said measurement device including a diameter determination unit for determining the diameter of the coil; and a controller for controlling the reciprocating movement of said traverse with respect to the rotation of said mandrel based on the measured diameter of said coil to wind said filamentary material on said mandrel in said coil of a figure-eight configuration to form said radial payout hole having a constant diameter, characterised in that said measurement device includes: a first sensor configured to measure a length of filamentary material wound about said mandrel, wherein said first sensor includes an encoder configured to generate a series of pulses corresponding to the length of filamentary material wound about said mandrel; and a second sensor configured to measure an angular displacement of said mandrel during the winding of the length of filamentary material about said mandrel, wherein said second sensor includes an encoder configured to generate a series of pulses corresponding to the angular displacement of said mandrel, wherein the diameter determination unit is configured to determine the diameter of the coil based on the quantity of pulses generated by said second sensor between two consecutive pulses generated by said first sensor. a first sensor configured to measure a length of filamentary material wound about said mandrel, wherein said first sensor includes an encoder configured to generate a series of pulses corresponding to the length of filamentary material wound about said mandrel; and a second sensor configured to measure an angular displacement of said mandrel during the winding of the length of filamentary material about said mandrel, wherein said second sensor includes an encoder configured to generate a series of pulses corresponding to the angular displacement of said mandrel, wherein the diameter determination unit is configured to determine the diameter of the coil based on the quantity of pulses generated by said second sensor between two consecutive pulses generated by said first sensor.