Fastener materials and grades
Sep 20, 2008
Clearwater, FL
Hello all,

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 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

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 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, 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.



Jul 8, 2008
Wayne National Forest
Yes that's a fine explanation everyone would do well to read and understand.

I've used alot of "Supertanium" brand threaded fastenings in my time and always had good luck with them. I used to be able to get about anything I wanted in grade 5 & 8 at Quality Farm & Fleet but Tractor Supply now does about as good at supplying those goods.

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
up north now
Grade 8 bolts are not used in the ultralight aircraft industry because they can be have purported to be "brittle" if used wrongly.

What can you comment on AN hardware? I have read/been told by "experts" it's the same as grade 5 in hardness. I also have been told it's "army/navy" hardware, and not aircraft specific.

AN hardware sure makes the use of fasteners easy!

Thanks in advance!
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Master Bike Builder & Forum Sponsor
Dec 28, 2007
Duvall, WA PNW
Pretty good - the rub on consumer purchased Grade 8 hardware is that it now often is imported and indeed not properly secondarily heat treated and is indeed more brittle than properly treated alloy. To say Grade 8 is too brittle or weaker or something like that is not correct when speaking generally, I agree.

I agree on paper about All-Thread. On the other hand decently procured M8x1.0 (when called for) makes excellent and stronger than necessary head studs for HT engines. They will last the lifetime of the rest of the engine.

Can you explain to the group about metric bolt grading.


New Member
Aug 4, 2008
Great info, I cut and pasted it to a word document for future reference ... always good to have input from "engineering"... thanks....
Sep 20, 2008
Clearwater, FL
A/N Hardware is Airforce/Navy spec.

here is a link: Aircraft Hardware - What You Need to Know

And yes it's amazing how much of the available hardware is made in China.

Pipe fittings, fasteners of all kinds, you name it.

I only use holochrome brand grade 8's in the shop. They are expensive compared to the foreign fasteners from the local supply, but I know what I'm getting.

I'm sure that foreign hardware varies in quality...the stuff I get locally appears to be good quality and I haven't had any problems.

The allens that I provide with my clutch actuator kit are undoubtedly foreign made.

I just prefer allens...we supply a 5mm wrench with the clutch actuator kit so that everything will be there i.e. (Our customers do not have to go out and buy a wrench to install our kit).

For this application it simply doesn't matter if the bolts have not been properly heat treated.

I'm no hardware expert...I just know what works for me.