Socket head cap screws...grade 5?

[Pennyman]

We are using Socket head cap screws (black oxide finish) for our suspension pivot points for accessibility reasons. The rulebook specifies SAE grade 5 or better for these.

I've seen some teams use them in the past (FEI) and I'm wondering if you verify the strength of these bolts in tech, as they have no head markings.

Help is appreciated!

[moose]

I believe most (or all) Black Oxide SHCS are the equivalent of grade 8 or higher. As long as you avoid the Stainless steel path, you should be ok.

[Drew Price]

If you can, buy them from a supply house and double check the catalogue and the packaging they come in, if you're nervous about it during tech bring the receipts and packaging with you.

They won't stop to help you verify the strength of the bolts in tech, the scrutineers will tell you... "Tough luck, go find some with markings, I have no way of knowing what those are." And they're right.




Originally posted by moose:
I believe most (or all) Black Oxide SHCS are the equivalent of grade 8 or higher.


I would be willing to bet money this is not true, there are plenty of SHCS's with head markings, sometimes in the form of a dot pattern since there obviously isn't room for the notches on hex head screws.

I also purchased several batches of black oxide SHCS's from Fastenal for the last car specifically that were SAE grade 5. It's printed on the bulk purchase bags and the boxes of the short bolts.

Best,
Drew

[Mike Cook]

I have a fastenal spec sheet sitting right here in front of me, as far as I know, most black oxide shcs's are grade 8 or better. Fastenals are:


Fastenal Product Specification Sheet
Alloy Steel Socket Head Cap Screws
Mechanical/Chemical Specification ASTM A574
Material Alloy Steel
Treatment Quenched and Tempered
Min Tensile #0 thru 1/2 in. 180,000 PSI
(See Mechanical Strengths) over 1/2 thru 2 in. 170,000 PSI
Proof Load #0 thru 1/2 in. 140,000 PSI
over 1/2 thru 2 in. 135,000 PSI
Min Yield 153,000 PSI (* required when equipment is not available for full-size testing)
Core Hardness #0 thru 1/2 in. Rockwell C39 to C45
over 1/2 thru 2 in. Rockwell C 37 to 45
Dimensions ANSI/ASME B18.3 (See Socket Head Cap Screw Dimensions)
Threads Class 3A, UNRC and UNRF series #0 thru 1-in.
Class 2A, UNRC and UNRF series over 1 thru 1-1/2 in.
Class 2A, UNRC series over 1-1/2 in.
Description/ Applications The socket head cap screw is an internally wrenched fastener designed for high tensile strength applications. Supplies greater tensile strength than equivalent size grade 5 or 8 hex cap screws. They are ideal for precision work with close tolerance and applications needing a well tooled appearance. Primarily they are used in tool and die fixturing applications because the head can be counterbored into a work piece to provide a smooth or flat surface.

[Drew Price]

Huh, thanks Mike, I will take a look at the labels on mine when I get to the shop later then, now you've got me curious.

I will stand by my hunch that it's possible to get Chinesium black-oxided SHCS's though, and even if it's safe to assume they're a high enough grade to use, make sure you can prove it to the tech inspectors, it's not even worth worrying about.

Best,
Drew

[moose]

I would certainly never reccomend getting crappy imported bolts - American made and tested ones are hardly that much more expensive in the scheme of things by the box; Plus the threads are always much cleaner. I've never noticed any dots, etc on SHCS - but I always ordered a high enough grade where I wasn't concerned.

[jrickert]

I would avoid any black oxide bolts if possible. They are not nearly as corrosion resistant as other coatings. I saw one team that used black oxide bolts in Michigan. Their car looked excellent at the beginning of the competition. By the last day every one of those bolts was covered in a film of rust.

[kapps]

As everyone said, at least the Fastenal one's are superior to grade 8. We buy most of our fasteners from Fastenal and I actually brought the printout to competition last year just incase they wanted us to prove it was grade 5+. Our Baja guys were telling stores of how they can't use socket heads because there's no way to prove what they are like hex bolts (no markings on head). I guess they're a little more strict checking fasteners when there's a definite chance that you will be airborne several times during the competition.

Fastenal brand socket heads follow ASTM A574. Grade 8 bolts follow SAE J429. If you have access to these specs (I have free access at my work), you will notice that the proof load for the socket heads is greater than that for grade 8 hex bolts by about 15%.