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Definition of Joint

JOINT: The junction of members or the edges of members which are to be joined or have been joined.

The following figures show various joints and it can be seen that an alternative description of a joint might refer to the “faying surfaces which are in contact”. While this is not entirely correct, it will assist the student in deciding on the joint which is present under certain conditions. Look at the joint shown in Figure 3.1 and at the same time, consider the definition of the work “joint” and also the “faying surfaces which are in contact”.


Now, look at Figure 3.2, the assembly consisting of three plates. Consider the number of joints and select your answer from the following:

  1. joint only?
  2.  joints?
  3. joints?
  4. joints?

Check your answer.


1 joint only No. You are thinking of one assembly which after welding will form one weldment. A weldment is an assembly whose component parts are joined by welding.
2 joints This answer is correct. The three plates form two joints. The actual joint is the faying area in contact with the centre plate.
3 joints No. You are considering three plates which form part of the assembly.
4 joints No. Perhaps you are considering each side of the joint. For example, there are four sides where fillet welds could be made. However, these are only two areas of faying surfaces.


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