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General | Types (Round head, flat head, ...) | Drives (phillips, torx, ...) | Nuts | Terms
The "Machinery's Handbook" categorizes fasteners as:
I could not find any official definition of Machine or Cap screw. The list in the table below is the way they were listed in "The Machinery's Handbook", but round and flat head were listed as both, the illustrations were similar to the ones above.
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Machine Screws hex round flat countersunk (82° & 100°) oval countersunk fillster |
Cap Screws round head flat countersunk fillster socket head button |
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Type:
TORX PLUS is an improved version of TORX® which extends tool life even further and permits greater torque transfer compared to TORX. Many screw drives, including Phillips, TORX, and Hexagonal, are also manufactured in tamper-resistant form. These typically have a pin protruding in the center of the screw head, necessitating a special tool for extraction.
Pozidriv® is very common in Europe. It looks a lot like a Phillips screwhead, but it includes 4 more contact points. Common sizes are Pozidriv¨ #0, #1, #2 and #3. With improvements in production tools to better control the torque of the tool the cam-out action is not necessary, and has very little purpose (except to aggravate people). The Pozidriv screws and drivers have straight sided flanks which are, not coincidentally, much more friendly for field servicing. With Pozidriv you can apply much more torque to the screw without having the driver bit jump out of the slot. Nuts:  Nuts - Hex Nuts, Cap Nuts, Wing Nuts, T-nuts - Bolt Depot Terms: (See also standards below) 12N - National 12 Pitch AN - World War II era hardware standards system. Literally "Air Force/Navy" or "Army/Navy." A very logical numbering system now being bastardized by government changeover to NAS/MS series. FT - Fine thread (same as UNF) FH - Flat Head HH - Hex Head HX - Hex Head MS - Military Standard specification National Coarse thread pitch (same as UNC) NF - National Fine thread pitch (same as UNF) NEF - National Extra Fine thread pitch NS - National Special thread pitch OH - Oval Head PH - Pan Head PH - Phillips Drive psi - Pounds per square inch. tpi - Threads per inch UNC - Unified National Course thread form (same as FT) UNF - Unified National Fine thread series
See:
links: Fastner Type Chart and Nuts at BoltDepot.com US & Metric Bolt Torque by Grade Screw Finder at BobbyDyer.com Screw Information at search.com Screwtypes at lara.com Fastener Material Chart at CenturyPerformance.com Metric Bolt Properties Grade, Strength Proof Loads at FullerMetric.com Strength at AtlanticFasteners.com ASTM, SAE AND ISO grade markings and mechanical properties for steel fasteners at AmericanFastener.com SAE Standards for Bolts CD Stud Fasteners Specifications at SunBeltWelding Tap Drill Sizes Corrosion Resistant Bolts at contractors-sources.com Aircraft Hardware Automotive Racing Products (ARP)- Bolts Stainles Steel fasteners with specs for Aluminum, Titanium also at ssina.com Fastener and Screw / Bolt Design, Formula and Calculation at Engineers Edge Strength Properties of Metals at EngineersEdge.com The Tempering of Martensite Types of bolts and screw heads. Fastener types. Fasteners 101 Home Depot Special Order Fasteners at CrownBolt.com
"The Nuts and Bolts of Bolting" by Joseph C. Dille Gardner-Westcott is a bolt manufacturer.
Pozidriv™ is a trademark of European Industrial Services Ltd.
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Machine Screw - Threaded all the way or a smaller shank allowing the screw to go all the way in.
Cap Screw - Typically only partially threaded with the solid part the same diameter as the outside of the threads (bolts),
Phillips screws and drivers have an intentional angle on the flanks so they will cam out of the slot before a power tool will twist off the screw head. This is (was) a creative production approach when the device was first invented, but it leaves a lot to be desired when it comes to field service of the screws.