Threads is a library designed to make threading under C++ simpler. It provides a "pthread" class, with an abstract method called "thread". It also provides classes for mutual exclusion of parallel processes and condition signalling, and a semaphore class that comes in handy when synchronizing constructor and threaded method.
Class 1 threads are a loose tolerance. Class 2 threads comprise 90% of stainless fittings and are normal commercial tolerance. Class 3 threads have a stricter tolerance and tighter fit such as socket cap and set screws. No definite relationship exists between tensile strength and tightness or looseness of fit. The symbol "A" added to threads, such as 2A, means external threads (screws), and "B" means internal (nuts).
They come in two main standards: English and Metric. In the Design Studio we use English sizes. The thread sizes that we use in the Design Studio are: #4-40, #6-32, #8-32, and #10-32. For example: The #6 in #6-32 refers to the diameter of the screw (witch is a reference to the wire size that the screw was made from) (smaller number - smaller diameter) and 32 witch refers to the number of threads per inch.