Googling around, the numbers I'm seeing for yield of AN fasteners are around 120 KSI. Which is really close to a Grade 8 fastener.
"Standard" AN bolts are slightly weaker than Grade #8. But, the dimensions, material, and overall quality of AN bolts are more consistent than SAE fasteners.
With no intention of adding drama. I am only speaking from personal experience and not from an engineering degree standpoint. But I would also like to point out that the original rivets are quite soft as are the perch bolts and various other structural parts of these types of cars.
Your question was could you use bolts,well yes you can! Now as far as the don"t weld on a frame .That myth is bullshit,I have shortened and lengthened frames on cars and trucks,old and newer stuff plated and welded and never had a problem.In most frames that you find with cracks from stress they 99% of the time start at a factory bolt hole,Next we"ll have the smart as engineers telling us to bolt our roll cages together instead of welding,well,I said it I"m done.
I used button head socket screws instead of rivets when I put a geuine k member into repop '32 rails. Worked great and looks like a rivet from a couple feet away. I think most of these replies are well meaning but exagerate the technicality of this issue. I can't remember eaxactly how many bolts on a side but maybe five so the compressive forces are really spread out. I'ts been about 10k miles on an un boxed frame and no sign of cracked paint or any other sigh of movement. BTW it's a flathead powered roadster.
I believe the assumption would be that you would torque the bolts to whatever is recommended for whatever size and grade of bolt you are using. Now that I've said that, I normally only torque things that REALLY need to be accurate (rod bolts, head bolts, mains, ring gear bolts, etc.) For anything outside of stuff like that, I tighten them by feel. I don't take the time to tighten the bolts that hold the water pump to the engine to a specific torque. Most bolts on a chassis I'll do the same. I just make them tight enough, and I suspect that most of the folks on this board do the same,
I once had a International semi with a steel frame, it had a factory sticker on it saying to never weld on it. Was it there to just save their asses? Probably.
I am not aware of a modern heavy truck that doesn't have frame rails made of heat treated or at least heat treatable material. Per my comments in post #47, field welding those materials can cause weakening/cracking.
Newer Mack truck frames have bolted on crossmembers,suspension hangers and so on.By bolted I mean a precision fastener with a head that breaks away when the proper torque is reached.I believe it's the design of the bolted on frame part,the fit of the bolts,the number of bolts ,is more important that if the bolt is grade 5 or 8. A large number of 1/4 inch bolts may be better than fewer 3/8 bolts......or not?
Mostly correct. It has more to do with the total cross sectional area of the sum of the bolts. In other words, if your design has more 1/4" bolts than your 3/8" design, it may be stronger if and only if the sum of areas of the bolting is greater. You also have to be aware of what the quantity and size of bolt holes does to the base metal. But the fact remains that for a given total cross sectional area of bolts, the grade 8 "grouping" will be stronger than the grade 5 "grouping."
The size and location of fasteners needs to match the requirements of the joint. Every joint is different, so no general rule applies. Although the concept of bolts is simple, there is a lot to know about bolts and their use. Like a lot of things, the more you learn about it, the more you realize how much there is to know. Unfortunately even some smart and knowledgeable people have perpetuated misunderstandings about fasteners. The last time I explained this here someone called me an asshole. Hopefully that doesn't happen again. Think of bolts not as rigid vise clamps but as springs. For a dynamically loaded joint to be stable, that spring clamping must exceed the force acting on the joint. That means the bolts must tightened until they behave like springs. There are joints where a higher strength bolt can't be tightened sufficiently to make it behave as a spring. In that case a weaker but fully tightened bolt could be better, or maybe a smaller high strength bolt would be used.
You are right. They did use soft bolts back in the day. I was just helping the Monday Night Engineers understand that things change and sometimes what was good for grandpa doesn't apply. Someone pointed out that every joint has its own set of rules per application which is also true, dead loads v live loads. Moment load all need to be taken into account when one is designing a structural part. But we are talking replacing rivets with bolts here, not designing the sears tower. Anyway no drama from you are just pointing out a truth. As long as you comb your hair and don't find corn in your comb you don't have a thing to worry about.
informative thread... good technical info. Larry, a while back I saw some cool fasteners that were basically bolts with heads in the shape of a frame rivet. They had a splined shoulder that would grab the inside of the hole in the frame so they wouldn't turn. That would look a lot better on the outside of your rails... If I find the link I'll send it to ya.
This is the thread that was discussing what I was thinking of: http://66.154.44.164/forum/showthread.php?t=509189&showall=1
Tempering is part of the heat trearting process. First the part is heat treated. That makes the part hard and more brittle. Tempering reduces hardness, but also reduces strength. Where the heat treating is pretty much all or nothing, tempering is adjustable/controllable. Tempering allows hardness/brittleness to be balanced against strength. Each material has different properties and reacts differenty to tempering. Engineers specify tempering based on charts that show hardness vs strength vs toughness. So as you can see, there is no such thing as "high temper" steel. Heat treated steel truck frames are made from a number of heat treatable alloy steels. There are cases where these steels are used un-heat treated. But you are right, whether they are heat treated or not, welding on flames made from these kinds of steels can cause problems.
3WLarry, I'm gonna be riveting in my replacement crossmember on the wagon. I like the look and the fact that the holes won't be opening up. Replacement cross members were bolted on, but the bolt heads don't let the fenders fit well.
Glad this came up. I may have to replace some studs on my daily (Chevy van) that are mounted to a bracket which bolts to the frame in 4 spots and is then riveted to the top of the spring pocket on the frame crossmember in 4 more spots. The crossmember is also bolted on in two places (you can unbolt the whole works from the van if you want). Sounds like I can probably replace the rivets with some grade 8 fine bolts and use some red Loctite on them and call it done. Because both pieces bolt to the frame rail in the same general area, I don't think they can move differently from one another very much. And if they do become an issue, I suppose I could have someone run a bead of weld to tie the bracket to the crossmember. (by the time those studs rot again the whole bottom of the van will have fallen off).
Not only are you correct, but the thing we've all lost sight of here is that the steel in the frame AROUND that bolt is likely only A-36 or equivalent, which is only 36,000 psi. The hole around the bolt will yield long before either a Grade 5 or Grade 8 bolt.
http://www.rockcrawler.com/techreports/fasteners/index.asp Someone was asking about relative shear strengths of grade 5 vs. grade 8 bolts. Above is a link to a technical article about it. It basically says that grade 8 bolts DO have a much higher shear strength than grade 5. As well as higher tensile strength.
I also always thought that the grade 8 was stronger so I was a little surprised when my MII kit from CE came with grade 5's. Made me a wee bit nervous so I went and bought the 8's just in case. But after reading all the above, I still have one question, why the hell are they still making grade 5? Is it for when you only want to be a little safe and grade 2 just wont do? Really, they are not that much more expensive- what's the purpose of grd 5? You either need it to be stronger or you don't- never a little stronger but not too strong.
You are thinking like a guy building one car. Having all of your bolts grade 8 might cost you an extra $5. No biggie. But, if you are building 100,000 cars, that equals a half a million dollars.
still cheaper than the lawsuit that you will get if one of your "save a nickel" bolts breaks and someone gets hurt. Bean counters are worse than Janet.
I'm sure there are applications for which a grade 5 is adequate, if not desirable. People use bolts for all kinds of things, not just on cars - we have a place here I go and buy by the pound when I need bolts for something and there's all kinds of things in there you'd never even see on a car.
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