Common problems in threading with straight thread: uneven horseshoe shape at the end, too short or too long threading, broken thread, poor diameter control, etc. Correction method: Workers need training before taking up their posts, and the horseshoe-shaped part at the end of the steel bar needs to be removed to calculate the threading length. After threading, check whether the threading is qualified with general gauge and plug gauge, and check whether the threading length meets the requirements. If the threading is incomplete, re-thread, and put on the thread head protection cap in time.