DML Final Exam Questions And Answers 2022/2023

Pitch Diameter - Answer - Sometimes called "mean diameter" is the diameter in between the major and minor diameter. It is the theoretical diameter at which each pitch is equally divided between threads. Pitch diameter can be thought of as the diameter at which the male and female thread should meet. It could be thought of as the working diameter. Name two ways to measure a thread. - Answer - Thread micrometer or three-wire thread measurement method. What is the rule of thumb for the length of internal thread to maximize the strength of the bolt? - Answer - The minimum recommended thread engagement for a screw in an assembly is as much as the screw diameter; a better assembly will result when 1 1/2 times the screw diameter is used. Describe when class two fits are used. - Answer - Class 2 threads are found on most screws, nuts, and bolts used in the manufacturing industry. Studs used on many types of machines are examples of class 3 fits. Describe UNC and UNF. - Answer - UNC stands for Unified National Coarse thread series and UNF stands for Unified National Fine thread series. Each has its own strengths. Fine is generally stronger in hard materials and coarse is generally stronger in soft materials. What is the formula for calculating the OD of a machine screw? - Answer - The formula is D=number of the machine screw x.013in. + .060in.; D=8 x .013in. + .060in. = .164in. What are setscrews used for? - Answer - Used to secure gears or pulleys to shafts. When are stud bolts used? - Answer - Can be used instead of long bolts. Often used to aid in the assembly of heavy parts by acting as guide pins. Describe the strength classification system and marking for bolts. - Answer - The strength grades of bolts are identified by the markings on the heads. The grade indicates the strength of the fastener. A manufacturer's chart may be used as a guide for proper torque of fasteners. Explain two reasons why flat washers are used. - Answer - Flat washers provide a larger contact area than nuts and screw heads to distribute the clamping pressure over a larger area. What is the purpose of a helical spring lock washer? - Answer - A helical spring lock washer prevents