In this machine the hollow spindle with the binder yarn is positioned between two pairs of cylinders, while a hook, below the spindle and rotating in the same direction, twists the core and effect yarn (Figure 1).

Fig. 1 Principle of the hollow spindle twisting machine

Given the intermediate position of the spindle – it is located between the pair of feeding cylinders and the pair of delivery cylinders – the twists imparted during this first stage are in the opposite direction between the first and second length of the two yarns.
The binder yarn runs inside the hollow spindle, parallel with the semi-processed core-effect yarn, as far as the twist hook, which makes it twist round the other two yarns, stabilising the product.
If the twist hook is driven as one with the spindle, and thus accomplishes the same number of rotations, the twists imparted to the core and effect yarn will number the same as the final binding twists. To prevent an excessively high number of twists making it necessary to stabilise the yarn with a steaming process, a separate hook twist drive has been developed that can rotate at a higher speed than the hollow spindle. The yarn is wound onto a package.