FAS­TEN UP

AU­TO­MO­TIVE FAS­TEN­ERS 101

NZ Performance Car - - Contents - WORDS: MAR­CUS GIB­SON / PHIL DEAN PHO­TOS: MAR­CUS GIB­SON

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.

SHANKED BOLTS

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.

SPRING WASH­ERS

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.

K-NUTS

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.

SCHNORR WASH­ERS

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.

NY­LOC NUTS

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.

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