Grade 9 bolts L9 or F-911.

Looking into Grade 9 bolts what’s the different between an F-911 and L9? From what I can tell there about the same, are there any web sites that talk about bolts in more detail?

Thanks in advance.

Xman

What do you want to use them for?

I think Fastenal (www.fastenal.com) has a good tech section, and checking out SPS/Unbrako and ARP's sites can prove helpful.

Again, I have to ask the application. While Grade9 bolts can be useful, they can also be used in entirely the wrong place or wrong application, and cause more trouble than you expected...

5-90

5-90 thanks for the info I'll check them out.

Application is for tie rods end (OTK Hiems) style looking for something strong but not brittle that will shear off. The F-911 has minimum 180,000 PSI tensile strengths.

Xman.

5-90 said:

What do you want to use them for?

I think Fastenal (www.fastenal.com) has a good tech section, and checking out SPS/Unbrako and ARP's sites can prove helpful.

Again, I have to ask the application. While Grade9 bolts can be useful, they can also be used in entirely the wrong place or wrong application, and cause more trouble than you expected...

5-90

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Point of diminishing returns - as something gets stronger, it also gets more brittle. Ductility and strength follow an inverse relationship.

I'd probably not go more than Grade8 in common stuff, or maybe check with ARP for some of their superalloy stuff (which is designed, from a metallurgical viewpoint, with your intended use in mind.) Also, checking with SPS/Unbrako would likely yield something better for you.

Frankly, I'd not use a 9 Grade for something loaded in shear like that (especially since I can almost guarantee you it will be in "single shear" - unless you forked the ends where the joints will go?)

5-90

higher grades are stronger no matter what....the "brittle" thing is totally misunderstood.

a grade 5 will fail before a grade 8 in tension and shear...*HOW* they fail is not worth debating.

Thanks for the info guys, anyone using F-911 or L9 on their steering setup, if so how is it working?

Xman

Prety much what Beezil said. I wouldn't bother with anything over grade 8 though. Questions is why? I don't think people are having problems with shearing bolts in their steering setups.

My tie rod set up is similar to the bulletproofsteering configuration. I want to make sure it won’t shear off. I’m sure the grade 8 will be fine but the F-911 has 180,000 PSI tensile strength not sure about a grade 8 or L-9, all the information I can fine (not much) seems the L-9 and F-911 bolts are about same.

Thanks,

Xman

sounds like a marketing gimick to me.

Weasel said:

sounds like a marketing gimick to me.

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Could you give more detail, way is it a gimmick?

Thanks,

Xman

as always correct me if I'm wrong but there arn't many problems with people breaking bolts on their sterring setups. Usualy the rod end go. This to me says that the common grade 8 bolt is strong enough when used in the correct size of course. Spend the extra money on some high end rod ends instead.

The reason I say Marketing gimmick is becuase it a very common stratagey used. List a bunch a high grade compents with really high numbers and it has to be better right? For example the Grade 9 bolt strength is listed in tension, what does that have to do with shear strength. Abosultly nothing as tensions and shear are not even the same forces. See what I'm saying? Wow the customer with great numbers and they will buy your stuff.

Correct. Tensile strength is loading in tension (pulling on the ends,) while shear strength is trying to pull thru the bolt sidewise. Shear strength is generally related to tensile strength, but is also considerably lower (I believe the common estimate is 60%, but I'd have to check my notes to be sure...)

If shear strength is really a factor, then the bolt profile will be designed for the application at hand. The threads and grip (non-threaded portion) will be so set up so that the threaded section will NEVER be loaded in shear - this is common with real racing hardware and AN/NAS hardware for aviation. No matter how well made, a thread is a stress riser and will create the initial failure point for the fastener. Therefore, it makes sense for the shear force to not be associated with the threads - the grip (which is also the full nominal diameter of the bolt, unless you are using a shoulder bolt) will be long enough to take the force, either in single shear (one shear plane) or double shear (two shear planes - thing running you ball rod end into a fork rather than laying it on something.)

Also, any critical shear joint, properly designed, will be loaded in a double shear setup, as splitting the shear forces will always maximise the shear strength of the bolt. It's a simple matter of load spreading, and can best be compared to picking up a 300# load - is it easier to do lonehanded or with a helper?

Granted, shear forces with conventional steering setups in pax vehicles aren't great, but if I were designing a rock monster or something that's going to be faced with some serious sidewise forces, I'd put some serious thought into the whole arrangement before I cut one part (and it's a cinch that I'd make most of the parts myself, just because I'm cranky and believe in overkill in engineering...)

5-90

Thanks for the info guys I really appreciate the input. :clap:

I found a F-911 specification sheet, but I don’t see anything that says Shear Tensile Strength, There is reference to Wedge Strength is this similar?

F-911 Spec.

Thanks,

Xman

"Tensile Strength" and "Shear Strength" are two different animals - tensile strength is the rating for the fastener when pulled endwise (calculated from the minimal diameter of the fastener body multiplied by the ksi/psi rating) and shear strength is the amount of pressure that the fastener can sustain when stressed sidewise - generally as a result of two parts that are able to move in relation to each other, and the "shear plane" is the zone in between the mating surfaces (and the shear plane is where the part will fail.)

Shear strength is estimated from the tensile strength, but is only accurate if it is a result of destructive testing. Shear strength is ALWAYS lower than tensile strength, but the shear strength of a fastener can be maximised through design and loading changes.

I have mentioned this in other threads, but an excellent book on the subject is Carroll SMith's _Nuts, Bolts, Fasteners, and Plumbing for Racing_ - it goes for sub-$20 at B&N...

5-90

xman said:

Thanks for the info guys I really appreciate the input. :clap:

I found a F-911 specification sheet, but I don’t see anything that says Shear Tensile Strength, There is reference to Wedge Strength is this similar?

F-911 Spec.

Thanks,

Xman

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5-90 said:

I have mentioned this in other threads, but an excellent book on the subject is Carroll SMith's _Nuts, Bolts, Fasteners, and Plumbing for Racing_ - it goes for sub-$20 at B&N...

5-90

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5-90,

Thanks for all the input, I will pick up that book.