Fastener materials and grades
I've been reading through some of the recent posts and saw some interesting comments regarding the fasteners that the chinese use to assemble their engines.
I've also read a few posts about the alternatives; Grade 8, Grade 5, even stainless.
Stainless is not a good choice for most applications...Stainless offers very little holding strength. Stainless is malleable...it will not take torque.
Stainless fasteners are used for finishing, and required, in applications where food items come in contact with machinery.
Stainless fasteners share the same stigma as titanium...most people think that titanium is lighter than aluminum and stronger than steel when in fact titanium sits nearly in the middle. Titanium is heavier than aluminum, lighter than steel: stronger than aluminum, not as strong as steel.
A lot of people also wrongly assume that stainless fasteners are the ultimate..."they are for the right application". They are more expensive, so the notion is that they must be better...just remember "better for what". Engine powered bikes need tough fasteners... unless you are seeking FDA approval leave the stainless out...lol.
The exception; dress-up items...stainless fasteners are fine for decoration.
DO NOT MIX STAINLESS WITH ALUMINUM...especially cast aluminum where heat is involved. Over time the materials will bond together making removal impossible. Wring them off and drill them out...so much fun!
The notion that grade "8" is too brittle and will prematurely fracture is also wrong. Grade "8" fasteners are made from chrome moly, (4130, 4140), heat treated to Rockwell 38-42 with a tensile strength of 140 to 190 PSI depending upon alloy and rockwell hardness.
Grade "8" fasteners are used throughout the racing world!
Grade 5 fasteners are fine as replacements for any of the hardware on the Chinese engines.
Chinese hardware...cheap, saw cut, all-thread for studs. All-thread never has been "high grade", it was manufactured as a temporary battle field "fix-it" during world war one. Cut off what you need and you have an instant bolt. The process of making all thread guarantees a low tensile stength product suited for emergency use...just as intended.
I use grade "8" allens for almost eveything, simply for the ease. I prefer an allen wrench to a screwdriver.