- - AGRICULTURAL CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2200) Unit Title: FASTENERS __________________________________________________________________________ (CLF2202) Topic: Selecting Fasteners Time Year(s) 3 Hours 1 / 2 / 3 / 4 __________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will will be able to: Learning Outcome #: (D-2) - Demonstrate the ability to select the proper fasteners and hardware for specific jobs or for situations encountered in agricultural mechanics projects. Special Materials and Equipment: Assortment of fasteners and associated hardware References: Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Editors of Reader's Digest. (1973). COMPLETE DO-IT- YOURSELF MANUAL (7th ed.). Pleasantville, NY: Reader's Digest Association. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th. ed.). Danville, IL: Interstate Publishers. Resources: Baumeister, T., & Avallone, E. A. (1987). Marks' STANDARD HANDBOOK FOR MECHANICAL ENGINEERS (9th ed.). New York: McGraw-Hill. Deere & Company. (1987). FASTENERS (3rd ed.) (Fundamentals of Service (FOS) Series). Available from: John Deere Technical Services, Dept. F, John Deere Road, Moline, IL 61265 (Available in Spanish) Oberg, Erik, Jones, F. D., & Horton, H. L. (1990). MACHINERY'S HANDBOOK (23rd ed.). New York: Industrial Press. Evaluation: Quiz by instructor. TOPIC PRESENTATION: Selecting Fasteners A. Specifications for Fasteners 1. Bolts a. Type (i.e., common, carriage, plow, etc.) b. Size 1) Diameter of the crest of the threads c. Length 1) Measured from the bottom of the bolt head to the end of the threads d. Threads 1) Specified by the number of threads per inch and by manufacturing tolerance of threads 2) Threads per Inch: a) UNC designated threads (coarse) are the most common in agricultural components. b) UNF (or SAE) designated threads (fine) are used in special conditions, for example, where parts being joined have thin walls. 3) Manufacturing tolerance (re fit) of threads. a) Thread class symbol such as 1A, 2A, etc. e. Grade (or property class) of bolts as delineated below: Grade Tensile Marking* Specification** Material Strength (psi) _______ _____________ ________ ______________ No lines SAE Grade 0 Low carbon steel No lines SAE Grade 1 Low carbon steel 60,000 No lines SAE Grade 2 Low carbon steel 74,000 3 lines SAE Grade 5 Medium carbon 120,000 steel, quenched and tempered 5 lines SAE Grade 7 Medium carbon 133,000 steel, quenched and tempered 6 lines SAE Grade 8 Medium carbon 150,000 alloy steel, quenched and tempered * Radial slashes on bolt head which are present on all bolts 1/4" or greater in diameter. ** Grades 2 and 5 are most common in agricultural equipment. Grade 8 is common to engines, power transmission, and other high loading conditions. f. Descriptive Symbols for Specifying Bolts 1) Example: 1/2 - 20 UNC - 2A X 3 where, 1/2 = Bolt size (diameter) in inches 20 = Number of threads per inch UN = Stands for Unified Screw Thread Standard C = Coarse thread 2A = Thread class (fit) symbol 3 = Length of bolt (inches) 2. Nuts a. Type (hexagonal, square, castellated, jam, wing, cap) b. Size 1) Diameter of the bolt to be used with the nut c. Threads 1) Same as for bolts, i.e., UNC or UNF 3. Washers a. Type (plain, lock, etc.) b. Actual inside diameter in inches c. Bolt size that will fit through the inner hole in inches 1) Actual hole is approximately 1/32" larger than the bolt diameter. d. Thickness of the washer in terms of the gauge of the metal that it is made from 4. Screws (less than 1/4" in diameter) a. Type (sheet metal, set, etc.) b. Size as specified below: Screw Approximate Number Diameter (in.) Fraction ____________________________________________ No. 2 0.086" >5/64" No. 3 0.099" >3/32" No. 4 0.112" >7/64" No. 5 0.125" 1/8" No. 6 0.138" >9/64" No. 8 0.164" >5/32" No. 10 0.190" >3/16" No. 12 0.216" <7/32" ____________________________________________ c. Length 1) Distance from the bottom of the screw head to the tip of the thread d. Number of Threads per Inch e. Head shape 1) Pan head 2) Flat head 3) Cross-recessed head (Phillips head) 4) Hex head 5) Allen socket head 6) Round head 7) Truss head 8) Oval head 9) Fillister head 5. Keys a. Type (square, Woodruff, etc.) 6. Studs a. Size in terms of the diameter b. Type of thread at each (stud and nut) end c. Thread length at each end of the stud d. Combined thread and "grip" length of the nut end 7. Pins a. Type (spring, dowel, etc.) b. Diameter of the pin c. Length of the pin 8. Rings a. Type (internal or external) b. Internal snap ring 1) Inside bore (hole) diameter 2) Groove diameter 3) Ring width c. External snap ring 1) Outside shaft diameter 2) Groove diameter 3) Ring width d. Spiral rings (internal and external) e. "C" and "D" rings (external) 9. Rivets a. Type (common, blind, etc.) b. Diameter c. Length 10. Adhesives a. Type (epoxy, PVA, silicone, mastic, etc.) b. Materials to be Joined 1) Read the instructions for use of the adhesive to be sure that it is effective on the materials to be joined 2) Request material safety data sheets. c. Environment 1) Read the instructions for use of the adhesive to be sure that it is effective in the environment in which the joined materials will be placed d. Holding Power 1) Strength provided by the bond e. Setting time f. Curing time 11. Nails a. Type (common, box, finishing, etc.) b. Nail size or length of the nail as designated by the term "penny" and written as, for example, a "10d nail" which designates a 3-inch nail. (The penny abbreviation "d" derives from the denarius, an early Roman coin.) 1) The length of common nails (through a 10 penny nail) can be determined by dividing the penny by 4 and adding 1/2." 2) For example, the length of a 6 penny nail is: a) 6/4 + 1/2 = 1-1/2" + 1/2" = 2 inches. c. Nail Shank Treatment 1) Bright nails are untreated. 2) "Cement" coated nails are actually coated with a resin. 3) Chemically etched nails are designed to provide a rougher shank surface. 4) Annularly threaded nails have circular threads around the shank to give a better grip than a bright nail. 5) Helically (spirally) threaded nails have screwlike threads about the shank. a) They hold better than bright nails and are commonly used to attach stair treads. 6) Helically barbed nails are deformed for greater withdrawal resistance. 7) Zinc coated nails are coated to provide stain and corrosion resistance but will also give greater gripping strength than bright nails. d. Nail Point 1) A variety of nail points are manufactured in order to allow for faster penetration or to reduce wood splitting. 2) Some of the nail points available include: a) Needle, pilot, chisel, wedge, blunt, long, etc. e. Nail Head 1) Head selection is primarily based upon the materials being attached, i.e., the softer the material the larger the head. 2) Finishing nails have a small head with a dimple to allow for countersinking. 3) When building forms or temporary structures, double headed nails will allow for quicker disassembly. 7/12/91 JWR/tf #%&C