External and internal threads can be produced. External threads should not to be positioned along the parting line of the mould. Internal threads require additional mould section or cores that have to be unscrewed before removing the part from the mould. Small, narrow threads can be obtained by the use of metal inserts which are introduced into the mould. During the heating/moulding process these are covered by the polymer. In the case of plastic inserts, they become joined onto part during the moulding process. Threads can be obtained:

• directly in the moulding: produced by a movable section inserted in the mould that reproduces the shape of the thread and the related dimensions. To obtain a part without faults, the following recommendations are to be followed at the time of the designing the product:

- pitch more than 4 mm

- threaded section with rounded shape