6-Point or 12-Point? The Case For ARP’s 12-Point Fasteners

Written by Bobby Kimbrough
02
An ARP 12-point bolt on top and a standard 6-point bolt on the bottom. The head size difference is very noticeable.

We often hear the heated debate between auto builders about 12-point and 6-point bolt heads and nuts. Both have their own pros and cons and arguments can be made for each. Yet, there are some applications where a 12-point bolt head or nut is clearly the smarter choice. Our friends at ARP Fasteners are experts at the subject having manufactured all types of fasteners for since 1969.

ARP Fasteners was the first company to design and engineer fasteners specifically for racing, developing many patented process for manufacturing high strength fasteners from very strong materials.

Our friends at ARP tell us that 12-point nuts on stainless studs are ideal for fastening exhaust headers on engine blocks. Using stainless 300 material, ARP Fasteners manufactures a stud and nut that is not affected by corrosion or extreme heat. Both are desirable properties for header mounting.

The 12-point nut is more compact than the typical 6-point hexagonal nut. Because the 12-point bolt heads or nuts are smaller, they will fit in smaller places, like close to a header pipe. Bolts or stud nuts on cylinder heads where large valve springs are used, space can be limited and the 12-point fasteners may provide a better fit.

03
The story of two 6-point fasteners and one 6-point socket with one 12-point socket.

Another common application for the smaller 12-point bolt heads deals with stroker engine builds where camshaft clearance can be a problem with connecting rod bolts. ARP 12-point connecting rod bolts offer much need space and help by taking off a little rod weight as well.

04
A 6-point socket should be used on 6-point fasteners and 12-point sockets on 12-point fasteners. As the illustration above shows, contact on 6-point fasteners used with a 12-point socket offers less contact area and is more likely to round off the head of the fastener with a lot of force is applied.

The 12 point design permits this style fastener to be tightened down with a 12-point socket wrench, permitting higher torques to be applied compared to a standard hex drive socket head fasteners.

ARP Fasteners points out that their studs and bolts come either black oxide chrome moly or Stainless 300 material. Both are nominally rated at 170,000 psi tensile strength which is substantially stronger than Grade 8 hardware.


This article is courtesy of Engine Labs