MAE 1351 EXAM 2 STUDY BOOK EXAM PREPARATIONS 2022/2023

MAE 1351 EXAM 2 STUDY BOOK EXAM PREPARATIONS 2022/2023 17.02 Screw Threads Screw Threads- helix or conical spiral formed on the external surface of a shaft. Form of common threads  Axis- A longitude centerline of the thread  Root-The bottom of the cut on external threads  Crest- The top of the external threads  Major Diameter- The largest diameter of a screw thread  Minor Diameter- The smallest diameter of a screw thread  Pitch diameter- An imaginary diameter measured from a point halfway between the major and minor diameters through the axis to a corresponding point on the opposite side.  Pitch- The distance from a point on a screw thread to a corresponding point on the next thread as measured parallel to the axis  Depth of thread- The distance between the crest and the root of a thread as measured perpendicular to the axis  Angle of thread- The included angle between the sides of the thread.  Body- That portion of a screw that is left unthreaded.  Chamfer- An angular relief at the last thread to help the thread engage more easily with a mating part. Applied to the first thread to help start a thread in its mating part.  Classes of threads- A designation of the amount of tolerance and allowance specified for a thread.  Fit-Identifies a range of threads tightness or looseness  Thread series-Groups of common major diameter and pitch characteristics determined by the number of threads per inch.  Lead- The distance a screw thread advances axially in one full turn. Single thread- composed of one continuous ridge Multiple threads- made up of two or more continuous ridges following side by side. ISO-International Organization for Standardization ANSI- American National Standards Institute. 17.03 Thread Cutting Tap-Cuts internal threads Die- Cuts external threads 2 kinds of holes:  Through holes- goes completely through an object.  Blind holes-a hole that does not go completely though an object. Tap set includes:  Taper tap-used to start a thread  Plug tap-used to thread through material or to thread a blind hole if full threads are not required all the way to the bottom  Bottom tap- used when threads are needed at the bottom of a blind hole 17.04 Modeling Screw Threads Two ways to represent threading  Schematic and simplified thread representation Exact shape is not needed in threading modeling and drawings, only indicate shape of the thread with a note. Schematic representation-shows the threads as a series of lines that are perpendicular to the thread axis. The crest of the thread is shown as a line across the full diameter of the shaft or hole and the root as a slightly shorter line that does not reach the full diameter. Simplified representation- shows the two major diameter of the shaft or hole and the threads as a dashed or hidden line parallel to the thread axis 17.06 Bolts and Nuts Bolt- a threaded fastener that passes completely through the parts and uses a nut to tighten or hold the parts together. Machine screws- threaded fasteners used for general assembly of machine parts and are specified by thread, length, and head type. Available in coarse (UNC) and fine (UNF). Cap screw- fine-finished machine screw that is typically used without a nut. Stud- fastener with different threads at each end. It is screwed into a threaded hole and holds other parts with a nut on its free end. Corse threads on one end and fine threads on the other end. Tool Runout- the distance a tool may go beyond the required full thread length. Set screw- used to prevent motion between mating parts, such as the hub of a pulley on a shaft. Hardened to make them stronger than the average fastener. Self-tapping screws-used to hold two or more mating parts when one of the parts becomes a fastening device. 17.07 Rivets Rivets- permanent fasteners that take the form of cylindrical pins with various shapes head. Two kinds of rivet joints:  Lap joints- parts overlap each other and are held together by one or more rows of rivets.  Butt joint-parts are butted and are held together by a cover plate or butt strap that is riveted to both parts. 17.08 Washers Washer- A flat disk with a center hole to allow a fastener to pass through