Optical comparators can visually inspect some of the key parameters of threads.
The methods for inspecting threads are as varied as the threads themselves. But for many thread components, experts say that optical comparators provide the best picture of thread quality.
Methods of thread inspection range from lasers to fixed and variable limit gaging. While no one method is best, optical comparators can visually show many of the key thread parameters. By profiling the magnified thread, the flank angle, which is the straight side that connects the tip or crest of the thread to its root, can be checked by a comparator. The minor diameter, the lowest point of a thread that touches the root, and the root's radius are two other parameters that can be inspected. The thread surface can be checked for burrs and imperfections with surface illumination.