A question of hardness

[glamourpets]

I am in the process of bolting my new axle onto my Boler frame. This seems like such a simple question. What nuts and bolts do I use? The old bolts are a little rusted, but they are in OK shape. I COULD use some anti-seize on them and recycle them. That said, they are rusting and probably of similar vintage to the axle I'm retiring. I could also go into a store like Home Depot or Canadian Tire and match the old nuts and bolts as close as possible. Will the Home Depot version have enough hardness to withstand the forces of this application? Home Depot sells nuts and bolts of all shapes and sizes, but they say nothing about hardness. *sigh* It seems like such a simple question. What should I do? Can anyone offer any wisdom on this matter?

Derek

PS If you followed the old thread, you know that the first axle was 1/4 inch too small. They replaced it at their cost and it appears that this one is the correct size. I'm just getting started on installing it, but we will see what happens from here.

[Thomas G.]

You should use grade 8 bolts for your axle. They are in a separate section at the big box stores and are more expensive. The cheapest place to buy them that I have found, is Tractor Supply, where they are sold by the pound.

If the old bolts just have surface rust you can probably reuse them.

[Bill in Pittsburgh]

Go with Thomas G's suggestion.
Don't be tempted by stainless as I saw someone do last summer trying to avoid rust.
NEVER use stainless in a high stress usage as they will eventually fail.

[Art VanDelay]

And use the BLUE thread lock fluid. Blue because you can get the nut off someday in the future. Red if you never want it to be removed. Use the thread lock even if you use a lock washer.

[Mike Magee]

Most bolts commonly sold are grade 5 hardness, IIRC. Grade 8 is the next step up. You can usually tell the grade by the number of raised lines radiating outward on the hex cap (top of the bolt). But I have forgotten how many lines mean which grade... anyone else know this?

PS-- after seeing the topic name, I'm glad this thread isn't x rated.

[Thomas G.]

Originally Posted by Mike Magee

Most bolts commonly sold are grade 5 hardness, IIRC. Grade 8 is the next step up. You can usually tell the grade by the number of raised lines radiating outward on the hex cap (top of the bolt). But I have forgotten how many lines mean which grade... anyone else know this?

PS-- after seeing the topic name, I'm glad this thread isn't x rated.

I believe that the common bolts sold are not even grade 5.

Here is a reference to the head markings. http://thermosealinc.com/THERMO_RESO..._Cross_Ref.pdf

[mmeyer]

Originally Posted by Bill in Pittsburgh

Go with Thomas G's suggestion.
Don't be tempted by stainless as I saw someone do last summer trying to avoid rust.
NEVER use stainless in a high stress usage as they will eventually fail.

Not to mention that if you don't use anti seize with SS nuts you will likely never get them off without breaking or cutting. Sometimes what you think is better can be a lot worse.
Michael J

[Raz]

Bill is quite correct about stainless steel. Depending on the alloy, I read it's about grade 2.

I recently bought my self a new torque wrench. While researching, I ran across an article that stated unless specified, applying grease, oil, thread lock, or anti seize all change the torque number. For those interested here is the torque article.
Torque wrench buyers guide

Finally, grade 8 SAE is equivalent to grade 10.9 metric as I recall.

[Ian G.]

I agree with all that has been said. Any suspension bolt must be Grade 8,
Also torque the bolt to the correct specifications, don't guess, attached is a Torque Chart for reference
Bolt Torque Chart

[Jared J]

Originally Posted by Bill in Pittsburgh

Go with Thomas G's suggestion.
Don't be tempted by stainless as I saw someone do last summer trying to avoid rust.
NEVER use stainless in a high stress usage as they will eventually fail.

I get your point, but that's somewhat inaccurate. Plain hardware store stainless fasteners, yes. I've used stainless fasteners that would make a grade 10 bolt look like nothing. You wouldn't want to pay for them, though.

Originally Posted by Art VanDelay

And use the BLUE thread lock fluid. Blue because you can get the nut off someday in the future. Red if you never want it to be removed. Use the thread lock even if you use a lock washer.

Properly tightened, not necessary at all.

Originally Posted by Ian G.

I agree with all that has been said. Any suspension bolt must be Grade 8,
Also torque the bolt to the correct specifications, don't guess, attached is a Torque Chart for reference
Bolt Torque Chart

Grade 8 won't hurt, and I probably would use it, but it wouldn't have to be, necessarily. There are many more factors than that. Fact is, a few decent size grade 5 bolts will have a yield strength much higher than most axles.

The bigger problem is chinese "grade 5,8 hardware", often isn't. tests have had some of them failing before U.S. grade 2 hardware. There are also good overseas suppliers, but buyer beware. Tractor supply has quality hardware, Horrible Fright has weak hardware.

[Bob Miller]

Take the old "slightly rusty" bolts and chuck them. They have been stressed for almost 40 years and the risk of using them to save a few $$$ is a bad investment!!!!! I suggest going to a "Real" hardware supply house and getting real grade-8 bolts (Meaning not Chinese Junque), your trailer is worth the investment.

[Raz]

Originally Posted by Ian G.

Also torque the bolt to the correct specifications, don't guess, attached is a Torque Chart for reference
Bolt Torque Chart

Great site, thank you. Raz

[Joe MacDonald]

try any local supplier like Northfast, Spaenaur, Rastall, they will have the bolts you need, and it won't be that expensive. I myself tend to use Nylock nuts, the ones with the little nylon insert that squeezes on the thread, that and a lock washer, and torque to spec, then forget about it, its done

Joe

[Steve Hilby]

Don't use stainless nuts with stainless bolts. I was amazed at how fast and firm they can seize. I spun a stainless nut by hand onto a stainless bolt once to check something, and the darn thing froze solid. I couldn't get it loose, even with a wrench, and eventually ended up throwing the bolt/nut away. It was quite surprising.

[mary and bob]

Grade 5 has three lines on the head.

[Raz]

Originally Posted by Steve Hilby

Don't use stainless nuts with stainless bolts. I was amazed at how fast and firm they can seize. I spun a stainless nut by hand onto a stainless bolt once to check something, and the darn thing froze solid. I couldn't get it loose, even with a wrench, and eventually ended up throwing the bolt/nut away. It was quite surprising.

Interesting, galling is usually associated with heat and tightening too tight. Perhaps they were different alloys? I have never had an issue and tend to use stainless a lot for low load applications. Raz

[David Tilston]

I have read that how fast you spin the nut affects galling. Slower is better. What I was reading referred to the use of power tools, so may not apply here. A grain of sand can also cause galling.

[Jared J]

Slower speed, boelube, or anti-seize. If they don't want to go together by hand, don't force it. If the threads are a bit off and you try to make it work, they will gall easily. I use a lot of stainless, and have very few problems. I've put thousands of them in (or out) in a single day at work.

[Bob Miller]

If you want stainless bolts to stay stainless you MUST use SS nuts. SS Bolts will quickly rust when mated with non-stainless nuts, washers etc. I can't say that I have ever had ss fasteners sieze though.... I don't think that's a common problem, but there is always anti-sieze compound to use if there is any concern.