Sorry, but as others have said, BS. Only in the last decade or so has heat treated steel been used in frames. Even the factory service manual for my 1986 Chevy truck describes how to WELD cracks in the frame. These frames are mild steel. Weld away. Somebody should explain to YOU how wrong that statement is. Why oh why does this statement keep coming up on automotive forums? Get yourself a copy of a Machinists Handbook or Mark's Handbook, or better yet, an engineering degree. Shear strength allowable for a bolt is approximately 60% of tensile. Grade 5 bolts have a tensile allowable of 120,000 psi, so the shear allowable is 72,000 psi. Grade 8 bolts have a tensile allowable of 150,000 psi, so the shear allowable is 90,000 psi. In what world is 90,000 less than 72,000? Also, BENDING load is NOT shear load. Bending in a bolt results in tensile failure, not shear failure. That's why spacers behind ring gears are a bad idea - they cause the bolts to bend. The bottom line is that a Grade 8 bolt is ALWAYS stronger than a Grade 5 bolt of the same size when loaded the same way. There's no if, and, or but about it.
My roadster came with a 35 rear crossmember bolted in the rivet holes that were cut out with a torch and I never noticed any problems but when I got it on a lift I welded it up. The fire wrench has made a mess out of a lot of frames in the 50-60s. I've saved a few that were axed up but never cared about rivets. I admire your attention to detail but I don't go quite that far.
A duece chassis isn't tempered steel. And as far as the Ford Class 8 truck is concerned there is just no excuse for poor craftsmanship. If the roll cage were properly built it wouldn't have come loose. As far as TV Tommy's car is concerned I am well aware that it was not built out of tempered steel, but I guess that makes your point of the engines being bolted in a mute point. Doesn't it. Never the less as you have stated But don't sweat it just put on peppermint shoes like the rest of us and go on with life. No one really cares and when you wake up in the morning you'll still have too many dollars and not enough sense. And to think I really thought that I could avoid the drama today. Who the hell am I fooling.
Right on Joe. An interesting note. In 1957 I attended a two week welding school at A.O Smith in Milwaukee. One day we toured their frame production facility. They took sheet stock in one end of the plant and finished frames came out the other. Now A.O.Smith was basically a welding machine manufacturer but morphed into products that were related or required welding such as stick welding rods, pipe, nuclear multi layered pressure vessels, silos, and car and truck frames. There were no rivets invoved.
What he said: with the biggest key to bolt strength being :"No threads in bearing", referring to no threads in the hole..........All shank, ( "That's what she said")
The transition to welded frames involved complete redesign from the open-channel ladder model...frames became various types of formed tubing and crossmembers were heavily triangulate with long welded areas...further, in cars, the body had become a significant structure adding strength to the longest spans of frame. Box a deuce frame and you are entering a different world with entirely different stresses! And the truck frames you cannot weld on...they are high tech steels, which would be severely altered with a high penetration weld...AND they are open channel, riveted, yes?
Bolt the SOB! Grade 8 would be best but 5 is ok too. I prefer bolted crossmembers, if anything gets bent or needs to be removed they are much easier to un-install than rivets. Big frame rivets are kind of a PITA until you figure out the process. Obviously, they hold fine as well. My vote goes toward bolts, however. If welding to a frame is bad then I suppose my Race car's roll cage is weakening the frame? I think as long as the penetration is good, welds would be an acceptable substitute, but I would use bolts. JB weld is pretty awesome stuff, but I think using it in conjunciton with hot glue would probably be much better. Adam
"Do you think its ok to weld on a 1946 Ford pickup frame? " No problem on that. Potential for problem comes from something that greatly stiffens a short section of frame while leaving the rest flexy. You can even see treatises on this in elderly body repair manuals...if you fishplate a simple channel frame as part of a wreck repair, you don't weld the plate all the way around...same reason.
So hey there 3W, what's the verdict? Looks like you've got more info than you bargained for. In the past I've mixed both. Added bolts with shanks to keep threads outta the critical area and then, just in case, added some short welds near the area. I felt it would help the bolts do their job easier and if it had to come apart later then a short time with a cutoff wheel and a couple blows with a hammer...voila. Off with no issues. 'beaner, nice try on curbing the drama but some things just happen no matter what. Ever go to avoid that thing falling off the bench or outta your hand and no matter what you do...
.......I would use high grade fine thread bolts.....rivets were use in the thirties for frames more for fast production on the line....also less workers error ....I also think a good weld would also work.......Like all hotrods bolts and welds should be check often...
WOW!...awholelotta info.....thanks guys maybe I should just ship the frame to Ionia and have Denny and Matt rerivet it.
Actually I have a rather worn copy of the machinist's handbook, probably from being a machinist for the last 16 years. What you have stated is right out an engineering book. Too bad it doesnt hold true. On anything frame related I would far rather have a bolt that will bend and not break.(Grade five) Harder bolts(Grade 8 and 12) will snap when stressed severly.
On something where the force is able to break a grade 8 or 12, the assertion is that it will only bend a 5? That confuses me. Can you elaborate? In using that theory, are you supposing that if the choice was between using an 8 or 12 you'd go 8 because that'd bend easier? Also, I'm thinking if there's a situation where the force is great enough to damage a grade 8 bolt, there's going to be issues elsewhere, besides the bolt, no?
Take the belly pan on a caterpillar. Grade 8 bolts break off when the belly pan is bent. They are a real bitch to drill out(ask me how I know this huh). The grade 5 bolts will bend and stretch quite a lot before they break off. Which do you want holding your frame together? For another example try tie rod end nuts. The right ones are pretty soft they are supposed to stretch before they fail. Hard stuff snaps soft metal will stretch before it fails. Welding the crosmembers in from the bottom is still probably the most sensible idea.
What you say is true in some cases, but not always. Some frames are made of materials that are adversely effected by welding. If the frame is heat treated the manufacturer may weld on it prior to heat treatment. You are taking your chances field welding on that type of frame, or one made from an alloy that is heat treatable. On a frame made of an alloy that can be safely welded, it matters where the weld is and how the weld is done. Manufacturers safely welding frames, subframes, and structural chassis pieces. I'm sure you believe what you posted, and posted it with the intention of beiong helpful. But as others have indicated, what you posted is a widely believed misconception. And, there is a lot more to this than what you indicated. Interesting to note, and exactly opposite of what was posted, when frame crossmembers in heavy trucks are replaced, manufacturers supply/recommend grade #8 bolts.
OK I have abstained from posting this in an effort to not ad more drama to this thread but here goes anyway. Take it as you will. In my last structural design class (about 4 years ago) it was stated that a grade 5 bolt was no longer considered to be a viable component in a high shear situation. It was mentioned that the although the grade 8 bolt was more brittle that the distortion factor of the grade 5 bolt was unacceptable and the benefits of the grade 8 bolt outweighed the grade 5 bolts. Structural theory changes with the addition of new data. I guess that is why to maintain a PE License one must have continuing education. I have some very old machinists handbooks and some newer one here. The older ones from the Ol' Man and the newer ones from when I worked as a machinist. It amazes me the changes in the books over the years. Anyway take it any way you like. I still would not be afraid to bolt the cross members in the chassis.
About 20 years ago, I had a '36 3 Window that someone had hacked up the front crossmember. I bought a new front cross member from, I believe, Precision Coachworks in Billerica, Massachsetts, and it came with both a set of rivets, and a set of button head fine thread bolts. Since I had more faith in my wrenching skills than my riveting skills, I used the bolts and red Loctite. I checked them for tightness a couple of times over the years, and when I sold the car abput 5 years ago, everything was still fine. Another advantage of the button head bolts was that after a judicious application of body filler and a litte sanding and some paint, the looked just like rivets, from the top anyway.
You should probably edit your other post to reflect *accurate* info. Your claims that: "One day somebody should explain to people that grade 8 bolt have a lower shear strength than grade 5. Grade 8 has a higher tensile strength but will break rather than bend when stressed sideways. Especially when stress is applied with two plates(Ie frame plates or cross members)" is NOT true.
This is the real world. Use the method that produces the best results for YOU. A good bolt is stronger than a bad weld or poor rivet. Final hole alignment in the real world is done with a tapered reamer called a "bridge reamer". Ream a hole - install a bolt & torque it down. Ream the next hole - install a bolt - repeat till there are no more holes.
I have owned the same Norton 850 motorcycle for thirtyseven years and seventyeight thousand miles, to kick start it I have to stand on the foot pegs and straight leg the kick start lever. The bike is standing on the side stand. The bolt through the side stand pivot has a washer on both ends and is double nutted to not vibrate off. It also has to be loose enough to allow the side stand to swing. When I had a Grade 8 bolt in that pivot it would snap off within a year. When I replaced it with a Grade 5 bolt, because I didn't have a Grade 8 handy, the bolts started to last for many years. This all happened before the import of junk Chinese hardware. Lots of shear on that bolt. Shear coincidence?????
Grade 8, Grade 5, Aircraft Quality... we won't be solving this debate here on the H.A.M.B. As a retired (as of July 2010) Mechanical Engineer I worked at manufacturing facilities my entire career. All the shops I worked at used combinations of welded joints and bolted joints. If I were to pick just one thing in my career that I thought was very simple that turned out to be very challenging is the science and engineering of bolted joints. There are people that make a good living doing nothing but consulting manufacturers in regards to failed bolted joints and what needs to be done to correct these failures. For whatever it is worth, on the vehicles I have built, when I have the option, I weld instead of bolt. One less thing to worry about.
Could be that your side stand was a loose fit thereby increasing the shear factor. Or it could just be that you were spending bucks on cheap import bolts or a combination of the two. I ran the same grade 8 bolt on the side stand of my Hawg for somewhere in the neighborhood of 200K. Bought it new from a bolt store when I first put the bike together. I had it down for an overhaul and while I was doing the machine work my old man saw that the bolt was pretty worn and he replaced it. I found it in his tool box when I inherited it. Funny the things the Ol'Man kept over the years. The cross members should be pulled up tight, not loose like a kickstand. There will be several in each end of the cross member to help keep it from walking. In theory the holes will be sized appropriately which also helps. I would be more comfortable with the grade 8s if it were my vehicle, they don't stretch as much. But if I were to run the softer bolt I would expect to re torque on occasion. All bolts stretch its just the nature of the beast. The softer bolts will have more tendency to stretch. Either will probably do the job just fine. Sometimes I loose my temper when I work on a hot rod, more often when I'm dealing with bolts than when I'm welding.
It has been my observation that high tensile strength material tends to have even greater yield strength. This translates to a "smaller" plastic region. In the case of grade 5 bolts, they will yield (deformation due to load is permanant) at 92K. They will continue taking stress for another 28K until they reach 120K where they will break. So 23% of their load carrying capacity is in the plastic region. Grade 8 on the other hand will yield at 130K. They will continue to take increase in load for another 20K until they reach 150K where they will break. This means that only 13% of their load carrying capacity is in the plastic region. So, from the time they start to yield until they break, grade 5 will take more load to reach the breaking point than grade 8. BUT the grade 8 will take 41% more load to reach yield and 25% more load to break. You could say that grade 5 gives you more "warning" between when they yield and when they break, but the grade 8 will yield at a higher load and break at a higher load than grade 5. And, as stated elsewhere in this tread, shear strength is approximately 60% of yield (although I tend to be conservative and use 50% in my calculations). (Also note that the strength values I used are the minimum allowable for the material. Your bolts may have higher strength values.)
The much more important information - and much easier for all to understand is this: Or, in even plainer English: the Grade 5 bolt is broken 10,000 PSI BEFORE the Grade 8 even starts yielding! There is no "opinion" about this. And obviously, as others have noted, the yield or shear allowable of the bolt is only ONE part of the proper design of a bolted joint. However, with all factors in the joint design the same, the Grade 8 will ALWAYS be stronger than the Grade 5.
Thanks redsdad!! That was really easy to understand. I just placed an order with Aircraft Spruce. Excellent inventory of AN fasteners.
Do they have strength charts available for the more readily available airframe bolts? That would be interesting...if not, off to the Carrol Smith book on fasteners. All this is beyond overkill for a hotrod frame, I think, but a handfull of bolts aren't going to cost that much, and better than SAE is reasonably available. I think filling the holes, that is bolts that will a bit of drilling out to get 360 fit, is good here. Note that a lot of the more important fasteners even in common production cars are not SAE graded...they are specials, formulated and treated for extreme toughness. SAE grades are illegal for aircraft use...
On an unboxed frame that flexes, I might rivet. On a frame that was boxed I would Bolt. On a frame that I assembled by welding it I would weld. The one thing that we seem to forget is that WE are assembling our own stuff, short of testing our assemblies on thousands of units all we can really do is inspect our own stuff regularly and replace any thing we feel not so comfy with.
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