Grade Determination

[kaiserman]

APPLICATION: Heavy duty trucks make use of king pins and bushings as part of their steering pivot points. The king pins are held in place with tapered threaded draw keys. Basically, the king pins have notches on their sides that allow a tapered draw key to be inserted and pounded in place. Then the draw key is secured in place with a locknut.

DESCRIPTION: Currently, we fabricate all of our own draw key hardware for the king pin kits we produce.
We purchase AISI 4140 rod material, fabricate it and heat treat it (surface hardness to 28 HRC to 34 HRC) to print specifications.

To date, not one complaint has ever arisen regarding draw key hardware failure.

That being said, our largest customer has recently specified that we must, among other things, place a grade on all of our hardware we produce for them to continue purchasing our products.

Now I am familiar with hardware grade markings and various hardware grade charts. However, I am very unfamiliar with the methods/specifications/standards used by hardware manufactures to establish a grade on hardware.

QUESTION: What method is used by hardware manufacturers to rate/specify bolt grades? Are standards available?

Thanks.

Regards,
Tim Kaiser
VW Kaiser Engineering, Inc.

http://www.vwkaiser.com

 

[TVP]

Yes, standards are available. You should review SAE J429 and SAE J1199 for externally threaded fasteners and SAE J995 for internally threaded fasteners. There are ISO standards available if you want a more international representation.

 

[Screwman]

Your hardness falls within the range of a grade 8 fastener, but you need to be careful if your product actually falls within the scope of what SAE considers a fastener. SAE J429 covers: "bolts, screws, studs, SEMS and U-bolts..."
I would have to really stretch my imagination to call what you are making a bolt or stud.
Spend some time and reasearch the specs to see if your product is within the scope of the the applicable specification. If you feel that it is not within the scope of the spec I would go back to your customer with the information you have gathered and explain why you feel the it would be wrong to to mark your product as Grade 8. If these parts fall under the Fastener Quality Act, mismarking them could make someone liable for a violation of federal law.

 

[dbooker630]

I would say that 28-34 HRC, if that is the core hardness also, falls outside the class 8 designation, which is 33-39 HRC.