Studs question (Not head studs)

[ChrisBennet]

The various 6 and 8mm studs used on Porsche engine are different than the studs I can get locally. The Porsche ones have a skinny "neck" or waist between the threaded ends. On normal studs, the unthreaded area's diameter is fat.
Can I use "normal" studs in the place of the Porsche ones?
TIA,
Chris

[Jim Sims]

If the studs are the same grade and the diameter of the unthreaded portion of the "normal" stud doesn't exceed the diameter across the thread crests they should interchange. Almost all male threads on smaller fasteners are rolled or upset using flat or planetary dies. The stud with the smaller diameter waist required more upsetting to produce the threads as it was formed from wire with a smaller original diameter. A stud's strength (if used properly in tension) is determined by the minimum cross-section which is the thread root diameter; this will be the same for both the thin and normal waist section studs. However, not all studs are equal; some forming dies do a better job of leaving the thread root material in a state of compression for better fatigue life. There is also a subsequent finishing operation (a roller pressed into the thread root and rolled along the thread) used to further condition the thread roots of studs and bolts used in severe duty service for improved fatigue life. I do not know if Porsche OEM studs have had this additional finishing operation; I doubt it as its probably not worth the expense. But you can never tell what a company that uses aluminum lug nuts might do! More than you wanted to read I'm sure. Cheers, Jim

[surflvr911sc]

My brain just sprung a leak! It never ceases to amaze me; the amount of knowledge floating around this board is mind-boggling. You can find out more info than your brain can handle on the most seemingly simple of subjects. Keep it up!

[ChrisBennet]

Thanks!