I need to create an M18 thread in a component in sketchup. How do I do it?
One way to do it is shown here. It shows Acme threads. Just change the profile.
You can use the Spirix plugin to use an M18 thread profile to create the threads. The video below is an example of creating an Acme thread, but the steps are the same … just a different profile.
There’s also a step-by-step here: 3D Printing Screw Threads
Be sure you really need a physical modeled thread as each one will add a huge amount of geometry to your file.
Often all that is needed is a texture.
@Box raises a good point: you need to consider the actual purpose of your model to make good decisions about what to model in detail vs what to “fake”. Another example is whether to use curves with large numbers of segments when the difference in visual appearance is negligible. It might matter if the model will be sent to a very high-precision 3D printer, but in almost all other cases will just bloat the model.
The amount of detail required is a good thing to consider. In the example I showed, the threads were drawn for 3D printing so the quality needed to be higher than it would if you are just representing a machine screw in a drawing.
You might be able to insinuate threads with a texture or, if you need to draw the threads, you can divide them up into smaller segments. The screw for this pipe clamp is really made up of a number of instances of a small, simple component. This keeps the file size reasonable and makes it easier to handle. It doesn’t cause the file bloat you’d see with the screw in my previous illustration.
It also makes for a screw which can very easily be adjusted for length.