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As I've started working on cars made during this century, I've started noticing that bits other than standard philips and flat head are being used. For instance, I needed an 8mm hex bit ( allen wrench style ) to open the calipers on a 2007 Mazda 3, and on a 2002 Nissan Almera I just bought I can't remove the steering wheel without a T50 size Tamper Proof Torx bit.

I see that in fact there are a wide variety of these odd ball so called "Security" bits:

odd ball bits

Which of these bits and in what sizes am I likely to run into working on modern cars? As bonus, what's the point of these "security" bits if any putz can buy them on Amazon?

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  • For VW/Audi cars you will need triple square bits (also larger sizes M8, M10, M12 and M14).
  • The main axle bolt on VW's is often a 19mm inhex head.
  • Opel uses Torx (Every size: from Tx15 up to Tx55) and external Torx (Mostly E12, E14 and E18). The engine mounting on a Meriva use a E16 that is very difficult to remove because of the missing space, so you need a E16 ring wrench (almost impossible to find).
  • Certain European head bolts use "ribe" heads.
  • There ought to be pentagon heads on Opel Astra G rear brake calipers.
  • The gearbox of VW/Audi cars uses a M16 triple square drain plug with a protruding pin.
  • For the freewheel of alternators you need a 33 teeth (certain brands a 31 teeth ?) interface.
  • All bets are off when you want to service "special" items like injection pumps, abs units, airbags and so on.
  • The oil drain plug of French cars ought to need a male 8mm or 10mm square (You can improvise it by detaching a common house door handle. Yes, at least at my place, there is a 8mm square inside it).
  • An early Renault 1.2 engine needs a very small 14 mm double hex socket for the spark plugs. An ordinary hex socket doesn't fit because the hole is too tight. (You can improvise a tool by rounding/grinding away of the edges of a 14mm tube spanner and weld a long bolt on the other end)
  • The French car manufactures really love to try things out and use some special sizes (M7 bolt with 11m hex head anyone?). (For some strange reason I like the French cars)

my recommendation

I would recommend you to buy a full 1/4" set of security bits (Also useful for household electronics). A 1/2" set of male hex sockets and a 1/2" set of male and female Torx sockets. Should you work on VW/Audi cars a full set of male Triple Square sockets is almost indispensable.

About the bits in your photo

  • First line: Phillips (metalworking, electronics), Pozidriv (woodworking), Slot (rarely used nowadays), Torx (ubiquitous: car, electronics, woodworking)
  • Second line: Security torx (MAF, sensors, others), Inhex (cars and Ikea furniture), Security inhex (found one once as a theft protection in a beamer wall holder), Robertson (I suppose they get used in North America?)
  • Third line: 2-hole, quad-wing, tri-wing and clutch (afaik all used in household electronics)
  • Last line: triple square (only found them in VW/Audis)
  • Why don't you integrate your comment on the OP into your answer? – Robert S. Barnes Mar 7 '17 at 6:54
  • The three-squares bit is popular within the VW empire. If the bolt isn't torqued down too tightly, you might be able to get away with a Torx bit. But there is every possibility that the head will round off and leave you with no option but to destroy the head in order to remove it – Zaid Mar 7 '17 at 7:43
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Hex (second row, second from the left in your image) and Torx (top row on the right) are widely used, because they are more suited for automated tools and/or are more resistant to deformation than flat-head and Philips.

(thanks to agentp for providing this paragraph) The "security" fasteners are often used not for "security" per se, but simply to stop the mechanic from accidentally removing a screw that shouldn't be removed. Even if he has the tool, it might make him stop and think "maybe I ought to go study the procedure first". The one in the steering wheel is undoubtedly there because of the air bag, with the presumption that anyone qualified to work on the air bag can get the proper tool.

Can't help you with sizes, other than noting I found lots of Torx screws, including a Torx T25 for the rear seat backrest in an Audi A3.

  • I'm guessing it's better to get the holed "security" versions since there's backwards compatible with the regular versions. So the only things you've ever encountered in the field are the hex and torx? – Robert S. Barnes Mar 6 '17 at 16:34
  • I'm not a professional mechanic, I only work on my own cars. So can't comment on which marques use which bit types. – Hobbes Mar 6 '17 at 18:11
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    special "security" fasteners are often used not for "security" per say, but simply to stop the mechanic from accidentally removing a screw that shouldn't be removed. Even if he has the tool it might make him stop and think "maybe I ought to go study the procedure first".. The one in the steering wheel is undoubtedly there because of the air bag, with the presumption that anyone qualified to work on the air bag can get the proper tool. – agentp Mar 6 '17 at 19:38

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