SAE J429 Grade 5 Hardware 1

[jnelson33]

Hello All,

I was looking at our parts here at work a few months ago and realized that there might've been a somewhat significant, overlooked detail during the early years of the company. We use Grade 5 screws with suspension parts. These suspension parts are sway bar end-links (see image). I know Grade 5 is okay in the right location on a vehicle's suspension system, but I am hesitant to say it's applicable for the primary hardware to be used with sway bar end-links.

Now, the type of person that I am means that I am looking at fastener designations on almost any product assembly that will show its goodies (cars, rockets, machinery, etc.); in simpler terms I am filing away design ideas based on their real world applications. I have always seen Grade 8 supplied with the parts kits that my dad and I would buy for our cars, but most people are not actually thinking about that stuff and just throw in the hardware that a person or website told them was the strongest. I know that most of the screws on my VW's suspension system are ISO 898 10.9+ for example, but my primary end-link hardware is ISO 12.9 I believe.

I've put in an hour or so trying to look for the data that I want, and I may have to buy SAE J429 or J1199, and I'm afraid that still may not answer it. All I was finding was very dumb info, like very dumb. Does anyone know if the SAE PDFs have true application data? Conversely, if you could shed some light of the efficacy of SAE Grade 5 vs Grade 8 for this application, then that would be great!

 

[GregLocock]

Don't get J429, all it talks about is details of the bolt itself. I don't have 1199.

Grade 5 loses about 20% on stress related properties, but has 2% more ductility, 14%


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[jnelson33]

Greg,

Thanks for shedding some light here. I will see if my roommate can pull J1199 from work first perhaps.

In as few words as possible; what are your general thoughts on that grade of fastener application?

 

[SwinnyGG]

SAE is not in the business of telling anyone what fastener to use for what.

There is no SAE document that is going to say 'use grade 3 bolts for attaching bumpers but use grade 8 bolts for attaching cylinder heads'.

It's up to the engineer to determine what fastener characteristics an application requires, and make an appropriate decision.

 

[jnelson33]

jgKRI that's understandable, but what I'm getting at is the info for SAE J429 Grade Whatever Metal vs ISO 898 Whatever Grade Metal is lacking overall.

I want the quick and dirty, generally, materials do/are used for this, but look out for this, etc and so forth. I didn't think that should be hard to find, but it doesn't surprise me.

Of course it's up to the engineer to decide, but since this is not a Lockheed Martin missile, I just want to make it the 1880's-1960's American Manufacturing way, or common-sense over-built to deliver the value the customer expects at the prices we charge. I promise you, I'm not mind-blowingly retarded, so let's keep the ever-resurfacing, "I think I'm somehow superior to you" engineer talk to a minimum.

If you have any thoughts on practical experiences with what I've wrote about, please reply with those as well.

 

[Tmoose]

Details of the installed arrangement are required for a thoughtful decision.
I'd expect the upper joint with the shouldered stud to have a few radial ratings by the manufacturer.

The bending the Grade 5 screw in the lower joint is subjected to is especially unclear.
If the lower joint is cantilevered way out at the end of the spacer, the diameter of the spacer may determine in large part the "strength" and stiffness of the assembly, if the screw is tightened adequately to keep the spacer from un-seating.

If either of the joints are attached to the flat un-reinforced sides of a stamped control arm , the control arm material may object to the wiggling and pulling, and show its unhappiness like this -

http://members.modernvespa.net/v_oodoo/uploads/plate_17550.jpg

http://forums.pelicanparts.com/uploads22/0113141026c+1+1389668148.jpg

 

[BUGGAR]

There are times when stronger is not better. A designer may want the bolt to be a lower grade so it will yield reasonably before letting go. Looking at Tmoose's fractured control arm is a possible case for the advantage of something bending visibly first.

 

[SwinnyGG]

so let's keep the ever-resurfacing, "I think I'm somehow superior to you" engineer talk to a minimum.

Who said anything about being superior? I'm attempting to help you.

What it appears you are asking, from your original post, is for a list or table that shows fastener types and grades next what they're commonly used for.

You won't find anything definitive from ISO, SAE, DIN, et. al, and for good reason- to try to categorize every possible fastener under every possible use case (or even a small subset) would take an enormous amount of time with no real benefit.

You should either use the experience you have in the world thus far to figure it out for yourself, or, if you are inexperienced, go back to first principles and figure it for yourself so that you gain experience.

The questions you are raising about this assembly that your company sells are reasonable, but they can and should be answered by looking at the work done in the design stage. Ask yourself why those particular decisions were made, as opposed to looking for a chart that proves whether you're right or wrong.

 

[Tmoose]

Sometimes I see, or am tempted to use Grade 8 hex head or alloy steel Socket head cap screws in the under-car environment here in Massachusetts with its salty wet 5 month long winters.

In those instances I just can't help but keep thinking that fasteners over HRC 40 are generally speaking more vulnerable to Environmental hydrogen embrittlement, and Grade 5s are something like HRC 30 max.

This effect is quite separate from the design of the bolted joint itself, where poor geometry can easily overwhelm exquisite materials.

 

[jnelson33]

I appreciate all of this information Tmoose, as it's exactly what I was looking for. Being that these are made to go on a Miata/MX-5, I do not believe Grade 8 should be used based on how the connection points look to be made on the car itself. I can go on to further investigate some of the other hardware now, but I generally like what you're talking about regarding destroying the car should it experience insane road forces, or a crash. I believe anyone will be happier if the car's attachment points maintain their shapes/positions/intended design and our part breaks first in the event of some accident.

 

[rickfischer51]

A couple of things might be worth considering:
1. Have you done any hand calculations to get a feel for actual loads? As a first pass you can approximate the stiffness of the sway bar by the torsional stiffness of the bar between the mounts. Then take the deflection of the sway bar with one wheel at full rebound and the other at full droop, and from these get an approximate shear force on the bolt. This would at least bound the problem. I think you need something like this before you start specing out fastener grades.
2. My guess is fatigue is a big part of this. Designing for a few cycles of impact load ignores the effect of hundreds of thousands of cycles of smaller loads.
3. You need to insure that shear or bending is not in the threaded portion of the bolt. Cant tell from the pic if that's true or not.
4. Pay attention to fastener torques. Remember the generic value of 0.2 for the torque coefficient K (as in T = K*D*F )is for dry unplated fasteners. it could b half that for a lubricated and plated fastener.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[Tmoose]

"I do not believe Grade 8 should be used based on how the connection points look to be made on the car itself."

Hi JNelson,

I was not dismissing SAE Grade 8 fasteners out-of-hand for New England under-car service. Or ≥ ISO 10.9.
What grade fasteners does the OEM use at those locations ?