16 as seen in fig2 the center strand 15 is displaced away from the center of the tendon 12 each bulbous portion 16 has a bulb diameter defined as the diameter of the smallest tube through which the rock anchor 10 will pass the bulb periphery is indicated by the broken lines marked 17 in fig2 the outer strands 14 and the center strand 15 are all located adjacent and within the bulb periphery 17 this enables cement to contact a greater surface area of the strands 14 in use as hereinbefore described the rock anchor 10 is thereby firmly embedded in the cement furthermore the center strand 15 is displaced away from its normal central position in the bulbous portions 16 when the rock anchor 10 is stressed the lead will be taken more evenly by the strands 14 and 15 than if the center strand 15 was in its central position if the center strand 15 was in its central position more lead would be taken by the center strand 15 than the outer strands 14 this would then lower the safety factor of the rock anchor 10 which could then fail at a much lower lead shown in fig3 is a first embodiment of an apparatus 20 for manufacturing a rock anchor 10 the apparatus 20 comprises a plurality of spaced clamp means 22 to clamp the tendon 12 the spacing between adjacent clamp means 22 is initially set at a first predetermined distance this first predetermined length corresponds to an uninterrupted length of tendon 12 necessary to form a bulbous portion 16 having the correct or desired proportions the clamp means 22 are slidably mounted.