6. Types of Threaded Joints

Threaded joints are specified below for the way a joint is made, or for its purpose.

Direct joints

The component parts to be joined have internal or external thread and are directly screwed together. No additional fastening elements are needed.

Figure 16. Direct joint

Indirect joints

The component parts to be joined are held together by standardized components, i.e. bolts, screws and nuts. Locking devices and washers may be used additionally.

Where a component part has a female thread, the joint may be made without a nut. The walls of the work-piece must be sufficiently thick for this kind of joint.

Figure 17. Indirect joint

Fastening joints

The component parts are to be joined directly or indirectly only for the purpose of connecting them. The vee-thread, ISO metric vee-thread or Whitworth thread, are the preferred types of thread. Both threads are self-retaining.

Figure 18. Screwed joint for fastening purpose

Adjustable joints

The component parts are joined for the purpose of connecting them and transmitting movements or forces. The preferred types of thread are round thread, acme standard screw thread or saw-tooth thread.

These are less self-retaining.

Figure 19. Adjustable joint

1 round thread, 2 acme standard screw thread, 3 saw-tooth thread

Name different types of threaded joints.