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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.
flat countersunk (82° & 100°)
Most head types come with a variety of drive types.
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.
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 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 - 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)
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
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.
Product Specifications at Barnhill Bolt
Understanding Threads and Fasteners at ivcc.edu (local copy)
Home Depot Special Order Fasteners at CrownBolt.com
Gardner-Westcott is a bolt manufacturer.
Pozidriv™ is a trademark of European Industrial Services Ltd.