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The "Machinery's Handbook" categorizes fasteners as:
I could not find any official definition of Machine or Cap screw. | |
Machine Screws hex round flat countersunk (82° & 100°) oval countersunk fillster |
Cap Screws round head flat countersunk fillster socket head button |
Drive Type:
Head Type:
Most head types come with a variety of drive types.
See: Screw head stripping is common when screwing into hard woods or when using Cordless screwdrivers and impact drivers: Phillip's head screws are actually designed to "cam out". That is, when the screw stops turning easily, the bit is pushed up and out of the screw head. This is to prevent you from over-torquing the screw and damaging the work, screw, or bit. When using impact drivers, phillip's heads are more prone to stripping. Pozidriv looks a lot like Phillip's, but has a subtly different shape that reduces cam-out.
Square, (aka Robertson) is easier to work with than Phillip's, but not as nice as Torx (aka star) & hex heads. Soap can help lubricate screws in to wood, making it easier and reducing screw breakage. See: How to Stop Stripping Screw Heads 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.
Phillips:
Fearson:
Pozidriv® is very common in Europe. It looks a lot like a Phillips screwhead, but it includes 4 small ribs in the groove. 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 UNF - Unified National Fine thread series (same as FT)
See:
links: BoltDepot.com - Nuts and Bolts, Screws and Fasteners online Head Styles - James Glen Wood and Sheet metal screws | Machine screws and bolts 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 screw drive systems at sizes.com Screw - Facts, Information, and Encyclopedia Reference article 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. Product Specifications at Barnhill Bolt Understanding Threads and Fasteners at ivcc.edu (local copy) 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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