Fasteners and Anchors

FASTENERS AND ANCHORS CONTREN Series # 40103-07 1.0.0 Introduction • Industry used a multitude of types of fasteners to assemble and install equipment, parts, and materials. • Industrial Maintenance personnel must be familiar with the different types of fasteners and their applications. 2.0.0 Threaded Fasteners • Most commonly used fastener. • Uses threads to hold parts together. • Terminology includes: – Nuts – Bolts – Screws 2.1.0 Thread Standards • Threads are manufactured to industry- established standards for uniformity. • Unified Standard (American Standard) – The most common thread standard. – Establishes thread series and thread classes. 2.1.1 Thread Series • Groups threads by pitch (threads per inch). • UNC – Unified National Coarse – General-purpose use • UNF – Unified National Fine – Finer threads for a tighter fit • UNEF – Unified National Extra Fine – For thin-wall tubes, nuts, ferrules, and couplings 2.1.2 Thread Classes • Groups threads by the degree of tolerance permitted. • Class A is for external threads (bolts) • Class B is for internal threads (nuts) 2.1.2 Thread Classes • Class 1A – loose fitting bolt threads – Used for quick and easy threading – Used in areas with high contamination – Maximum clearance on bolt threads • Class 2A – bolt threads with nominal clearance – Most commonly used thread class for bolts • Class 3A – tight fitting bolt threads – Used when precision fit is required – Threads must be very clean – Minimum clearance on bolt threads 2.1.2 Thread Classes • Class 1B – loose fitting nut threads – Used for quick and easy threading – Used in areas with high contamination – Maximum clearance on nut threads • Class 2B – nut threads with nominal clearance – Most commonly used thread class for nuts • Class 3B – tight fitting nut threads – Used when precision fit is required – Threads must be very clean – Minimum clearance on nut threads 2.1.3 Thread Identification ¾ - 10 UNC – 2A - LH (1) (2) (3) (4) (5) 1. Nominal size – Approximate diameter of fastener ( fractional) 2. TPI - Threads per Inch (Pitch) – Each nominal diameter has a standard number of threads per inch per series 3. Thread Series Symbol – Indicates the unified standard thread series – (UNC, UNF, UNEF) 4. Thread Class Symbol – Indicates the closeness of fit between the bolt threads (1A,2A, 3A) and the nut threads (1B, 2B, 3B) 5. Left Hand Thread Symbol – Used ONLY if threads are left-handed 2.1.4 Thread Design • Unified Standard Threads – Standard thread design for most all common bolts and nuts – Used primarily to hold parts together 2.1.4 Thread Design • Power Transmission Threads – Used to move machine parts for the purpose of adjusting, setting, or transmitting power. – Not typically used to hold parts together. • The following three thread designs are the most common Power Transmission Threads 2.1.4 Thread Design • Buttress Threads – One side of thread is cut square, the other side has a slant – Great strength along thread axis in one direction only – Used extensively to screw thin tubular parts together 2.1.4 Thread Design • Square Threads – Strongest thread – Threads have parallel sides – Hard to machine 2.1.4 Thread Design • Acme Threads • Easier to machine than the square thread • Almost as strong as the square thread 2.1.5 Grade Markings • Markings on the head of the bolt to signify the quality of the bolt. • SAE (Society of Automotive Engineers) • ASTM (American Society for Testing and Materials International) – Established these standards • The greater the number of marks, the higher the quality of the bolt. 2.1.5 Grade Markings No Marks 3 Marks SAE Grade 1 SAE Grade 5 SAE Grade 2 ASTM A449 ASTM A307 Medium Carbon Low Carbon Tempered 74,000 psi 120,000 psi 5 Marks 6 Marks SAE Grade 7 SAE Grade 8 Medium Carbon ASTM A354 Quenched & Tempered Medium Carbon 133,000 psi Quenched & Tempered 150,000 psi 2.2.0 Bolt and Screw Types • Made in a variety of shapes • Made from a variety of materials • Identified by the head type 2.2.1 Machine Screws • Used for general assembly • Size range from very small to ½” diameter Slotted Phillips Pozidriv Torx Hex (Allen) Clutch Robertson 2.2.1 Machine Screws • Head designations PAN HEAD FILLISTER HEAD FLAT HEAD TRUSS HEAD OVAL HEAD ROUND HEAD 2.2.2 Machine Bolts • Used for assembly where close tolerances are not required. • Size range from ¼” to 3”. • Normally have a square (4 sides) or hexagonal (6 sides) head. 2.2.3 Cap Screws • Used on high-quality assemblies where a finished appearance is required 2.2.4 Setscrews • Made of heat-treated steel • Used to lock pulleys and gears on shafts to prevent slipping Flat (Half-Dog) Cone Cup Oval Knurled Full (Full-Dog) 2.2.5 Stud Bolts • Threaded on both ends • Screwed into a tapped hole in the back part with a nut on the other end holding the front part tight against the back part • Thread Rod is a type that is threaded along the full length of the stud 2.3.0 Nuts • Different configurations for different applications • Usually, most are hexagonal or square coupling nut regular hex nut regular square nut flange nut 2.3.1 Jam Nut • Used to lock a standard nut in place on a bolt or stud bolt • Typically, about half the height of a regular nut jam nut regular hex nut 2.3.2 Castellated, Slotted, and Self-Locking Nuts • Used in critical applications where the nut cannot be allowed to loosen bolt cuts threads in cotter pin placed through the nylon insert slot and hole in bolt nylon locking nut slotted nut deformation causes thread interference cotter pin placed through slot and hole in bolt castle nut self-locking nut 2.3.3 Acorn Nuts • Used when appearance is important • Used when safety is important by covering the sharp threads on the end of the bolt or stud cap (acorn) nut 2.3.4 Wing Nut • Used for rapid tightening and loosening by hand only wing nut 2.4.0 Washers • Fits under the bolt head or nut • Used to enlarge the area of force onto the work piece • Lock washers also prohibits loosening of the bolt or nut 2.4.1 Lock Washers • Designed to keep the bolt or nut from working loose External (Greatest Resistance) Internal Split-Ring Internal - External Countersunk Ribbed 2.4.2 Flat and Fender Washers • Flat washer spreads the load over a larger area • Fender Washers forms a bridge over a large hole Cone Washer Flat Washer Fender Washer -for appearance -for oversized holes Wedge Washer Shoulder Washer Wave Washer -for angled surface -for insulation -for preloading 2.5.0 Installing Threaded Fasteners • Assure proper hole size for the type of bolt • Torque bolt and nut to correct setting • Use safety wire or cotter pin, if required • Most important, use correct grade of bolt 3.0.0 Non-Threaded Fasteners • There are many other fastening devices that are not threaded • Retainers • Pins • Clamps • Rivets • Tie Wraps 3.1.0 Retainer Fasteners • Internal and external holding Non-Groove Fasteners Groove Fasteners Internal Self-Locking Ring Internal Retaining Ring External Retaining Ring Spiral Ring E Ring External Self-Locking Ring 3.2.0 Keys • A keyway slot is cut in the shaft and the component to be locked to it. • A key is inserted into the keyway Square Key Gib Head Key Woodruff Key Pratt & Whitney Key (Semi-Circular) 3.3.0 Pin Fasteners • Long, circular fasteners • Dowel Pins • Taper Pins • Spring Pins • Cotter Pins 3.3.1 Dowel Pins • Precise positioning of mating parts • Grooved pins have a higher holding capability due to spring action of the grooves 3.3.2 Taper and Spring Pins • Normally used to lock gears, pulleys, etc onto a shaft • The taper allows for a tight “wedge” fit • Spring (Roll) pins compress into the hole, creating a very tight fit Taper Pin Spring Pin 3.3.3 Cotter Pins • Usually inserted through a hole drilled crosswise through the shaft • Used to keep components from falling off the shaft Cotter Pin Shaft Lock Spread ends apart Hitch Pin Pull Loop to keep cotter pin from backing out 3.4.0 Blind / Pop Rivets • Ideal fastener for fastening when only one side of the joint can be reached. 3.5.0 Tie Wraps • Self-locking strap (usually nylon) to fasten bundles of cables or wires together 4.0.0 Special Fasteners • Threaded fasteners designed for a specific application. • Eye Bolts • Thread Inserts • Panel and Electrical Mounts 4.1.0 Eye Bolts • Has a loop (eye) on one end for attaching lifting cables or for cable or wire guides Swivel Eye Bolt Plain Eye Bolt Shoulder Eye Bolt 4.2.0 Thread Inserts • Provides high strength threads in soft material • Replaces damaged or stripped threads in tapped holes Heli-Coil Thread Inserts This end goes in first. E-Z Lock Insertion tool grips Thread this prong. Inserts 4.3.0 Panel and Electrical Mounts • Stamped from sheet metal • Clips to panels for attaching components J-nut G-nut regular nut attached Cage Nut U-nut Regular nut caged in a spring clip 5.0.0 Mechanical Anchors • Used to attach components to a material that cannot tapped or the back side is unreachable • One-Step Anchors • Bolt Anchors • Screw Anchors • Self-Drilling Anchors 5.1.0 One-Step Anchors • Driven through the component to be anchored and the hole in the substrate at the same time • Wedge Anchors • Stud Bolt Anchors • Sleeve Anchors • One-Piece Anchors • Hammer-Set Anchors • Threaded Rod Anchors 5.1.1 Wedge Anchors • Comes with a wedge on the bottom and a nut and washer on the top • Anchor is driven through the component hole into the substrate hole and tightened with the nut 5.1.2 Stud Bolt Anchors • Depth of hole is critical • Threaded wedge is driven down onto the taper to lock it into place 5.1.3 Sleeve Anchors • Comes with a wedge

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