               - - AGRICULTURAL CORE CURRICULUM - -

(CLF2000) Advanced Core Cluster:   AGRICULTURAL MECHANICS

 (CLF2200) Unit Title: FASTENERS

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(CLF2201) Topic: TYPES AND USES OF            Time            Year(s)
                 FASTENERS                  2 hours       1 / 2 / 3 / 4
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          Topic Objectives: Upon completion of this lesson the student will
                             will be able to:

          Learning Outcome #:

             (D-1) - Identify five samples of each of the various fasteners 
                       used in power, metal fabrication, and structures.

          Special Materials and Equipment: Assortment of fasteners and
                       materials to fasten together

          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: Types and Uses of Fasteners

A. Importance of Fasteners

   1. They simplify the manufacture of machines and structures.
       a. Fasteners reduce the need for large one-piece parts; it is
           normally much simpler to make less complex components and fasten
           them together.

   2. They simplify repair of structures and equipment.

       a. Individual component parts can simply and quickly be separated 
           for inspection, repair, or replacement.

   3. They provide safety.

       a. Use of fasteners tends to assure that once an assembly is fastened 
           together it will hold together. They can be installed to provide
           additional support or they can be the weak link that prevents 
           dangerous major equipment failures (for example, shear pins on 
           driveshafts and breakaway plowshares). 

B. General Types of Fasteners

   1. Bolts, Nuts, and Washers

   2. Screws

   3. Keys

   4. Studs

   5. Pins

   6. Rings

   7. Rivets

   8. Adhesives

   9. Nails

C. Specific Types and Uses of Fasteners

   1. Bolts are threaded lengths of steel rod with heads on one end; they 
       are used with a nut at the other end and sometimes with a washer as
       well.

       a. American Standard (Hexagonal or Square-head) Bolts

           1) Most bolts have a hexagonal (6-sided) head although some older 
               bolts have a square (4-sided) head.

           2) Bolts are used with flat washers to fasten wood parts together
               and with or without lock washers to hold steel parts together.

           3) Without a nut they are called cap screws and are used by 
               screwing into a threaded hole.

           4) Bolts are often selected by strength rating and/or chemical or
               temperature compatibility.
       b. Carriage Bolts

           1) Most have a round head with a square neck under the head 
               although some have a flat, countersunk head; still others
               have finned or ribbed necks.

           2) Carriage bolts are used to fasten wood parts or steel parts
               with square punched holes where a smooth finish is desired.

       c. Plow Bolts (countersunk, square-neck carriage bolt)

           1) These have flat, tapered heads that fit into countersunk holes 
               in plowshares or other similar parts.

           2) Plow bolts are used when it is necessary for the head to lie 
               flush with the surface of the part, for example, attaching 
               cultivator shovels to a standard and all components of a 
               moldboard plowshare.

   2. Nuts are flat, usually hexagonally-shaped steel pieces with internally 
       cut threads that are screwed onto the threads of bolts.

       b. Square nuts are also common; knurled round nuts are less common.

       c. Jam Nuts

           1) These are normally thinner than hex and square nuts and used 
               to lock a standard nut into place by running up against the
               hex or square nut.

           2) They are commonly used where vibration or cyclic loads
               may cause a bolt to unscrew.

       d. Castellated and Slotted Nuts

           1) These are hexagonal nuts with slots in the sides which 
               resemble in appearance the walls of a castle that has been 
               slotted for archers.

           2) These are used when a cotter pin is placed through a hole in 
               the bolt to secure the nut so it cannot come loose, for 
               example, on wheel bearing spindles.

       e. Self-locking Nuts

           1) Once tightened, these nuts stay firmly in place.

           2) They are commonly known as "elastic," prevailing-torque, or 
               plastic-insert nuts.

           3) They take the place of nuts with jam nuts and are generally
               more compact.

   3. Washers

       a. Plain washers (flat washers) are steel disks with a hole in the 
           center.

           1) They are used to reduce the stress under a bolt or nut.

           2) They spread the clamping force from the bolt over a larger
               area as would be needed with wood. They also span slots and
               oversize holes.

       b. Lock Washers

           1) Helical spring washers are made of tough, spring steel and 
               normally installed under the nut (but they can also be used 
               under the bolt, particularly cap screws).

               a) The dimensions are specified like a plain washer.

               b) They are used to prevent rotation of the nut.

           2) Toothed ("shakeproof") lock washers give special holding power 
               because the many sharp, heat-treated teeth to dig into the 
               surfaces pressing against them.

               a) They may have external, internal, or external/internal 
                   teeth.

               b) They offer greater contact area to protect parts and 
                   provide a flat mating surface.

   4. Screws are threaded lengths of steel rod with heads on one end.

       a. Screw heads may be slotted for common screwdrivers, cross 
           slotted for Phillips screwdrivers, square or hexagonally 
           shaped for wrenches or other shapes described below.

       b. Sheet metal screws are also known as thread-forming or tapping 
           screws.

           1) They are used to attach light, thin parts made of sheet metal, 
               soft metal castings, plywood, fiberglass, plastics, etc.

           2) The screw forms its own threads in the parts that it is 
               screwed into.

       c. Set screws are used to hold a collar, pulley, gear, etc. on a 
           rotating shaft and in fractional horsepower applications; they
           prevent relative rotation between the two.

           1) They commonly have a hex (Allen) socket head but may also have
               a square or slotted head.

           2) A variety of point (tip) styles are available, ranging from 
               cupped to flat to cone-shaped.

           3) Set screws are not an especially strong type of fastener and 
               will normally score or raise a burr on the shaft which may 
               make the part held to the shaft difficult to remove. Use of a
               flat or cavity on the shaft will prevent this.
       d. Hex socket cap screws have a hole in the head of the screw made to 
           fit a hex (Allen) wrench.

           1) They are used in recessed holes or in confined spaces where 
               the small head size may be an advantage.

       e. 12-point flange-head screws have external teeth around the heads 
           to allow use of a small 12-point box-end wrench.

           2) These are used where small-diameter, high-strength screws are 
               required, for example, on hydraulic motors.

   5. Keys are square, rectangular, or semicircular-shaped steel pieces that
       are commonly used to hold a gear, pulley, or other part from rotating 
       on a shaft.

       a. Both the shaft and the part to be held have a groove (keyway) cut 
           into them.

       b. A Woodruff (semi-circular) key extends deeper into the shaft and 
           and tends to eliminate "rocking" that may occur with square or 
           rectangular keys.

   6. Studs are steel rods with threads on both ends.

       a. One end is screwed into a part, while other parts are assembled 
           over the stud and secured in place with a nut.

           1) For example, studs are commonly used to attach the head of 
               the engine to the engine block.

       b. Many studs have coarse ("interference") threads on one end and 
           fine threads on the other.

           1) The coarse threads go into the pilot hole and compress when 
               screwed in to create the locking action.

   7. Pins

       a. Spring pins (rollpins) are hollow cylinders of spring steel which 
           are split lengthwise and chamfered at both ends.

           1) They are made slightly oversize so they compress when driven 
               or pressed into place.

           2) They are frequently used to secure items to shafts for both 
               thrust and rotary loads.

       b. Dowel pins are solid round steel pins used to assure that the 
           fastened parts align exactly as they are designed.

           1) The diameter of the dowel pin is slightly larger (0.0002" 
               over) than that of the hole it is to be driven into.

       c. Quick-lock pins are square-shaped pins with a spring-like circular 
           wire piece at one end which serves as an overcenter clip.
           1) They are commonly found on 3-point hitches of tractors and 
               implements.

   8. Snap rings provide removable shoulders to accurately locate, retain, 
       or lock components together against thrust loads.

       a. Internal snap rings fit inside grooves in holes.

       b. External snap rings fit inside grooves on shafts.

   9. Rivets are soft metal pins with heads on one end.

       a. The common solid rivet is used primarily to hold two or more flat 
           parallel parts together, for example, sheet metal parts and 
           sickle sections on mower cutter bars.

       b. The blind (pop) rivet can be installed in a joint which is 
           accessible from one side only, for example, sheet metal boxes or 
           enclosures and for sheet metal patches.

           1) Blind rivets are intended for light duty only.

  10. Adhesives are glue-like materials which are spread on the two 
       surfaces to be joined.

       a. Adhesives are used to join dissimilar materials or complex parts 
           which would otherwise be difficult to join with conventional 
           fasteners or welding techniques.

       b. Most adhesives are affected by the environment in which they 
           are used and their strength may be adversely affected by
           temperature and exposure to moisture or other liquids.

       c. There are limitations to what materials may be effectively
           bonded with a specific adhesive, i.e., the "universal" 
           adhesive does not exist.

       b. Epoxy 

           1) It is composed of two parts, a resin and a hardener, that must
               be mixed together.

           2) It is excellent for general repairs but can be expensive.

           3) Epoxy is commonly used on non-porous materials like metals and 
               ceramics; it can also be used on woods and fabrics but they 
               can as easily and cheaply be held together with white glue.

       c. PVA (polyvinyl resin adhesive) Adhesives

           1) A common example of PVA adhesives is white glue (such as 
               Elmer's) that comes in a bottle ready to use.


           2) White glue is suited to most interior woodworking and 
               household repair jobs where high strength and dampness are not 
               factors.

        d. Resorcinal and Formaldehyde

           1) Both adhesives are excellent for bonding wood to wood where
               structural strength is required.

           2) Both require mixing, resorcinal with a resin and formaldehyde 
               with water.

           3) Formaldhyde is recommended for indoor use only due to its poor 
               weather resistance qualities.

           4) Resorcinal can be used in exterior applications due its 
               superior resistance to water.

       e. Silicone is used primarily as a sealing material in gaskets found 
           in high temperature applications (up to 400 degrees F.). Room 
           temperature vulcanizing (RTV) silicone is used for calking and 
           making positive seals when used with conventional gaskets.

           1) It is water and oil resistant.

       f. Mastic

           1) Synthetic latex mastic is water-based.

           2) Rubber resin mastic is essentially synthetic rubbers in a 
               solvent.

           3) Both materials bond well to concrete, hardboard, asphalt, 
               leathers, textiles, and ceramic tile.

           4) Masic is used for roof patching, asphalt sealing, and securing 
               plywood panels to dry walls.

  11. Nails

       a. Nails are steel rods with a head on one end and usually pointed at 
           the other end. They are used primarily to join wood together.

       b. Common Nail

           1) This is a general purpose construction nail suitable for 
               framing of structures. It has a larger diameter than the same 
               size box nail.

       c. Box Nail

           1) Box nails are used for end nailing and light household use.

           2) The point is dulled to prevent splitting of wood.

           3) It has a smaller diameter than a common nail to help avoid 
               splitting.
       d. Finishing Nail

           1) This is a nail with a small head with a dimple in the center 
               to allow for countersinking with a nail set.

           2) Countersunk finishing nails are used in cabinetry or
               paneling.

       e. Duplex (double headed) Nail

           1) A duplex nail has two heads on the shank.

           2) It is used whenever the nail is to be removed, for example, in
               assembling concrete forms.

       f. Wire Staple

           1) This is a "U" shaped nail.

           2) It is used in fence construction and electrical wiring.

       h. Roofing Nail

           1) This nail is used to secure shingles or roofing to the 
               underlying structure; it has an oversized head.

           2) They are normally available with either a spiral or 
               helix-threaded shank for extra holding power.

       i. Flooring Nail

           1) It is used to fasten hardwood floorboards.

           2) It has a plain shank between the head and threads and can be 
               installed with a floor nailing machine.







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