AUTOMOTIVE FASTENERS 101
UNDERSTANDING WHAT FASTENER TO USE WHERE CAN MEAN THE DIFFERENCE BETWEEN A RELIABLE BUILD AND ONE THAT’S ALWAYS UP ON JACK STANDS. WE TALK WITH AUTOMOTIVE FASTENER EXPERT PHIL DEAN OF KEY WEST BOLT AND SUPPLY TO GET THE LOW-DOWN ON WHAT OPTIONS ARE AVAILABLE FOR AUTOMOTIVE APPLICATIONS. NORD-LOCKS, CONE LOCKS, K-NUTS, AND BLACK-STEEL CAP SCREWS — BUILD YOUR CAR ONCE AND BUILD IT RIGHT
COPPER-COATED LOCKING NUTS Perfect for applications such as manifolds, these are top locking with an ovaled thread. Copper-coated steel ensures that they do not seize, which is a common occurrence with uncoated steel nuts. These nuts are available in sizes M6–M10 and are often used in conjunction with a grade-nine washer on a screw in stud for exhaust manifolds.
These are used in high-stress applications such as suspension. The strength of shanked bolts lies in the shanked unthreaded part of the bolt, and your local cert man will require at least 80 per cent shank through the bush or joint. It’s worth noting that at least three full threads will need to show past the nut.
BRASS MANIFOLD NUTS
Although these are not locking nuts, the brass is able to shrink and expand with heat cycles and does a great job of holding tension. These were popular in early cars, and your grandad probably used them in his flathead builds. However, they are not common in modern applications.
SERRATED FLANGE NUTS
Flanged steel nuts with a serrated flange surface, these are great in locations such as non-turbo exhaust manifolds and a great replacement for a spring washer–flat washer combo when mild heat will be experienced. They are popular in carb-tomanifold studs, or anywhere that there is not enough thread to have a locking washer. The serration bites into the surface to hold tension. These are a multi-use nut.
The most common and cost-effective anti-vibration washer, the classic spring washer should be used anywhere that parts are continuously serviced, as it can be used over and over. A spring washer should never be used where heat is present, as it will lose its tension. A spring washer is commonly used with a flat washer as a combo but can also be used alone. You can also get reduced-circumference versions that are perfect for use with cap screws.
When it comes to extreme heat locations such as downpipe V-bands, wastegates, and two-piece brake rotors, it's hard to go past K-nuts — flanged and ovaled locking nuts but with reduced hex size, which makes them extremely lightweight. High-temp versions are cadmium plated, although non-high-temp black-steel variants are also available.
8.8 VERSUS 10.9 BOLTS
Stamped on the head of our hardware will be a rating. Any high-stress areas will require at least an 8.8-rated bolt, although 10.9 will usually be used in areas such as caliper mounts. If your car is going to be certified, all hardware will need to be from a local recognized supplier, and data sheets might be required to prove that the hardware is as it says on the head.
These are in the same family as Nord-Lock washers, although they are one-piece cup-style anti-vibration washers. Once tightened, the washer will flatten and the serration will bite into the surface. Used extensively in OEM suspension/steering, etc., these are cheaper and easier to assemble than Nord-Lock washers, and the bolt-length variation is not as great. There is no correct orientation as to how the cone should sit; it will work either way.
Probably the best-known locking nuts, nylocs are constructed from steel with a small amount of untapped nylon that holds the tension once threaded. They are used anywhere that heat is not an issue. Like cone locks, these should be replaced after a single use — yes, we are all guilty of reusing.
CONE LOCK NUTS
A member of the top lock family in which the thread has been distorted slightly after manufacture, steel cone lock nuts are used in non-heat applications, popular in suspension and drivelines. One thing to note is that these are considered one use and should be replaced as soon as they become easier to thread, as repeated use will cut the thread to the point at which they no longer hold tension.
BLACK-STEEL CAP SCREWS
While not the prettiest bolts on the market, as they go rusty quickly, black-steel cap screws are commonly used in race car applications for their strength, being 12.9. A zinc-coated version will have lost 12 per cent of its strength through the pickling process, as it de-tensiles the bolt. The longer that it’s held in the bath, the weaker it becomes. This is also something to take into consideration when having your old hardware zinced; going new is advisable, if possible.