4 main earth systems

Types of Bolt and Screw HeadsPan Head:Reccomended fornew designs to replce round,truss, and binding heads. Provides a low, large diameter head, but characteristically high outer edge along the outerperipheryof the headwhere driving action is most effective for high tightening torques. Slightly differenthead contour wheresupplied with recessedhead. (see dotted line)Flat Head: Supplied tostandard dimensions with an80o to82oangle to be used where finished surfaces require aflush fasteningunit. The countersunk portion offersgood centering possibilities.Round Head: Not recommendedfornew design(see pan head). This headwas the most universally useddesign in the past.Oval Head: Fully specified as "oval countersunk", this head is identical to the standardflat head, but posesses, in addition, a rounded, neat appearingupper surface for attractiveness of design.Fillister Head: The standard oval fillister headhas a smaller diameter than the round head, but is higher with a correspondingly deeper slot. The smaller diameterhead increases the pressure applied on the smaller area and can be assembled close to flanges and raised surfaces. Headed incounterboreddies to insure concentricity, they may be usedsuccessfully in counterbored holes.Binding Head (Straight Side): Mostgenerally used inelectrical and radio work because of its identifying undercut beneath the head, which binds and eliminates fraying of stranded wire. Offers an attractively designed, medium-lowhead with ordinarily sufficient bearing surface. Notordinarilyrecommended as a Phillips Recessed head, see pan headforbetter functional design.Truss Head:Alsoknown as oven head, stove head, and oval binding head. A low, neat appearing, large indiameter headhaving excellent designqualities, and as illustrated canbeusedto cover large diameter clearance holes in sheet metal when additional play in assembly tolerance is required. Suggest panhead as substitute.Holt Head (patented): Provides the perfecttamper proofassembly. Theft Proof, decorative, and inexpensive. Special drivers available for field removal or power drivenassemblymachines.One-Way Head: This ingenious tamper-proof type of head, once assembled, cannotbe removed but isdrivenwith a standard screwdriver. Manufactures with amazing economy inproductive quantities, this simple design canfrequently solve costly assembly problems.Philips Finishing Washer Head: Designed as a neat appearance product for the electronic and appliance trade withall threadedstyles.Washer Head:This design has the finished appearance of a conventional roundhead plus washer and was originally created to provide extra large bearing surface under the head. The modern "truss" head(carried in stock)normally answers thispurpose.When a largediameter isrequired this washerhead
design isrecommended.Flat and Oval Heads (undercut): This is the standard flat or oval head 80o to82o countersunk screwwhichhas the lowerone-third of hte countersunkportion removed to facilitate productionof extremely short lengths. As illustrated, it will fit a standard counterboredhole and is particularly adaptable toflushassemblies i thin stock.Flat Head (100o Countersunk): This special flat head screw has been developed for applications requiring flush surfaces, and is recommended for use in soft materials to distribute pressure over a larger and less angular surface. Verywelladaptedfor use with thin aluminum, softplastics, etc.Square Shoulder Screws: An adaptationof the standard carriage bolt design. Possesses a truss headon a square shank which resists rotation when located or driveninto place. This squareshoulder may also be staked into place as a permanent fastener. A great many varieties in all screw diameters are available in productive quantities.Indented Hexagon: Aninexpensive wrench headfastenermade to standard hexagon dimensions. The hex is completelycoldupset in a counterboreddie and possesses an identifyingdepression in the top surfaceof the head.Indented Hexagon Washer Head:Produced in the samemanner as thestandard indented hexagon head butwith awasher section in the base of the head to protect the finish of the assembly from wrenchdisfigurement.Acorn Head (Full Undercut): A veryneat appearing trimscrew for appliance application - excellent wrench surfaces.Hexagon Head (Trimmed):This is the standard type of wrench-appliedhexagon head, characterizedby clean, sharp corners trimmed to close tolerances. Recommended for generalapplications, it is available in all standardpatterns and in all thread diameters.Head Styles (Welding Screws): The welding screw has been developed toprovide a strong, permanent threaded fastenerwhichbecomes a integral part of the assembly. It utilizes the principle of projection weldingbymeans ofmultiplelugsapplied tovarious head surfaces. Type "U" (Underlug): For general application. Assembles easily into prelocatedholes and fully utilizes head strength. Top surfaces of head designated for efficient welding anode contact.Flat Head styles takefull advantage of the self-centeringfeature of the countersunk portion and provide a smooth, flushouter surface.Type "T" (Overlug):for applications requiring smooth, finished outer surfaces. Under surface of head is designed for perfect electrode contact.