Hello again, Having now found the screw threads, and edited them and admired them from many different angles, I find myself having a blonde moment... When you create a screw thread, it draws a ring to represent some of the dimensions of the thread. My question to you the world in general, is does this line represent the largest/smallest diameter of the thread, or is it the pitch diameter? For example, I would like to make two components which screw together. The outside diameter of the inner piece and inside diameter of the outta is 35mm. When applying a (BSI) thread to the outta, a 35mm diameter selection will only allow me to select a 39x2 thread minimum, and the line drawn on the model has a diameter of 39. On the inner, I can select a 36x2 thread, but the line drawn has a diameter of 33.8mm which as far as i know is the pitch diameter of a 36x3 thread. Can't can I just model two pieces that mate up, and apply a possitive and negative M36x2 thread to both sides? Confused.
The drafting standard (ASME and ISO) for displaying internal threads is to show a solid line that represents the tap drill used before the threads are tapped and a dotted or phantom line to show the theoretical OD of the threads. For external threads the OD of the part (solid line) and the Minor diameter (dotted line) of the threads are shown. The pitch diameter is not normally represented. The dimensions of the thread are given as the OD and the Pitch or Lead. Metric treads give the Lead. Imperial or SAE threads give the Pitch or threads per unit length.
