Screws and Bolts

Slotted or Blade
  • Oldest style of screw
  • screw head is easily mangled
  • screwdrivers are simple to create if needed
  • sometimes has a second slot 90 degrees to the first because of that easily mangled factor
  • normal screwdriver blades taper along their length, gunsmithing screwdrivers should have parallel sided blades.
  • the width of the blade and the thickness of the base of the blade increases as screw size increases
  • the de facto standard in Canada for electrical equipment and most wood screws
  • colour coded:
    Orange#1,#2 you will probably never see one of these
    Yellow #3,#4 rare, used in small wood screws
    Green #5-#7 common as dirt
    Red #8-#10 common for the bigger dirt
    Black #12, rarish, used in big wood screws
    Brown 5/16, 3/8 you will probably never see one of these
  • Americans have square drive (Robertson was patented and they didn't want to pay the fees). Square drive is not quite compatible with Robertson, Robertson screws have slightly rounded corners and the screwdrivers have a slight taper to hold the screws tightly, the American copies will work, just not nicely.
Hex or Allen keys
  • used for everything from Ikea furniture to bicycles to very large heavy equipment
  • available in both metric and imperial sizes where the size is the distance between any two parallel flats
  • the metric sizes run from 0.7mm to 46mm and imperial from 7/64" to 3/4"
  • ball end hex keys are available to allow access to sockets where you can only get in at an angle
  • security hex bolts have a pin sticking up in the middle of the socket
  • originally designed so the driver would "cam out" of the screw at a specified torque during assembly, or that could be an urban legend and it is just a poor design
  • sizes are:
    0000 ridiculously tiny electronics stuff
    000 tiny electronics stuff
    00 very small electronics stuff
    0 #0, #1 Small electronics stuff
    1 #2-#4 lots of things
    2 #5-#9 vast numbers of things
    3 #10-#16 smaller numbers of larger things
    4 #18-#24 rare
  • easily confused with the next three screw types
JIS B 1012
  • Japanese screw that looks like a Philips but has very different geometry
  • often has a dot or cross in one corner of the screw but this is not guaranteed
  • the screws are common on lots of Japanese equipment especially motorcycles but the screwdrivers are hard to find in North America
Frearson or Reed and Prince
  • sharper edges than a Philips
  • relatively rare now so you hopefully do not have to care but this is a possibility if none of your Philips, JIS or pozi drivers work right
  • looks like a Philips with an extra X
  • this is why your Philips screw driver never works correctly to assemble Ikea stuff
Torx or hexalobular (guess which name people actually use)
  • very common in electronics and automotive applications
  • E-torx is the same thing only the screw head is male and the screwdriver or socket is female
  • like security hex keys security torx screws have a stud sticking out in the middle of the screw, there is also a five point security torx as well
  • torx sizing goes from T1 to T100 and E-torx goes from E2 to E44, confusingly the E sizes and T sizes are not the same so a T30 would fit on an E8
Triple Square or XZN
  • three overlapping squares at a 30 degree angle to each other
  • common on newer German vehicles in high torque applications (VW/Audi brakes for example)
  • sized from M4 up to M18
Spline drive
  • used in high torque applications on engines and aviation
  • used in some air brakes and agricultural equipment
Polydrive or RIBE
  • used in automotive high torque applications
  • mostly Italian and some German equipment (you'll need some for your Ferrari)
Square Head Bolt
  • these are often found on very old equipment and for whatever reason air compressor heads
  • mostly imperial and can be unfastened with an open ended wrench, crescent wrench or with a 12 point socket, eight point sockets also exist but are very rare
Hex Head Bolt
  • this is probably what you think of when you hear bolt
  • can be metric, imperial or on old British vehicles, Whitworth
  • right now every country in the world is metric except the United States, Liberia and Myanmar (AKA Burma)
  • American vehicles have been very nearly 100% metric for the fasteners since the 90's (although that is not necessarily true for the threads). In the 80's and 90's many/most American vehicles had a mix of metric and imperial fasteners as subassemblies were redesigned over time and before that they were pretty all imperial sizes
  • Japanese metric threads have the same profile but not necessarily the same pitch as European threads for the same size bolt and for the same bolt diameter, the head size will probably be different
  • On old German stuff you could pretty much get away with only owning the odd numbered wrenches (5,9,13,15,17,19,21mm), you could often get away with only owning the even numbered wrenches on Japanese stuff but with newer stuff this is a less safe assumption than it once was
  • metric wrenches go up in one millimetre increments with the addition of occasionally needing a 3.2mm and 5.5mm wrench
  • imperial wrenches go up in 1/16" increments with some old speciality applications using 5,7,9,11,19,21, or 25 /32" wrenches

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