When replaceing frame rivits with bolts, what type and why?

 

As in all the rivets holding everything together?

Garbz

 

I've always used bolts that barely fit the holes (the sames size as the rivets) Grade 8 bolts for relocating cross members and installing drop hangers...

 

I have been told not to use the grade 8 because of the shear factor with the twist of the frame. Is that true?

 

I've never had one break...

 

My Uncle was a chasis mechanic his whole life and I asked him this question number of years ago. He said to use the hardest bolt I could get and drill out the rivit hole to an interference fit (press fit).

 

Generally accepted method of determining sheer is approximately 60% of tensil strength. However there are so many variables that it really is application and load type specific.
All that said, I would go with(and did) grade 8. IIRC that is a Ø1/2" bolt. You'll have a whole lot more to worry about before either grade shears.

 

Thank you guys. I'm going to go with the grade 8s because like you said, I'm going to have a lot more to worry about before i shear any of those.

 

Shearing would be the least of your worries if it ever happens.

Mitch

 

As I recall, my experience has been that nearly all the bolts that have sheared or broke were those that were not tightened properly.

Thus, don't forget to use a lock washer, lock nut, or a chemical thread locker with your fasteners.
I'd also use the recommended torque for the size of bolt being used less 20% when using a thread lube (never-seize) or thread locker, such as "blue" loctite.
Below is a link to a good Bolt Torque Chart (2nd page down):

http://www.imperialinc.com/pdf/A_Fas...rqueCharts.pdf

(I printed the page and taped it inside the lid of my tool box so that it is close at hand.)
BarnieTrk

 

Bolting a 61 to 65 frame together is a bad idea as it must have a degree of flex, it must flex when loaded. It is not an issue with transmission mounts or other mounting points.

Modern trucks have gone to more rigid full welded and hydro formed frames to avoid flex but the suspension components and mounting points are engineered to handle the flex loads.

Brackets that hold the suspension components to the frame do not flex but apply the forces to the rails and they in turn have a bit of flex built in to them so the do not break and crack

Bolts are made to restrain in tension not shear. the flex of a frame adds side load at the head and grade eight bolts will fail.

OEM and aftermarket weld or riveted frames for this reason. No aftermarket frame builder bolts them together for this reason.

Garbz

 

Garbz,
I understand what you're saying and agree to a point.

HOWEVER, I'm thinking that the issue of necessary frame flex is more of a concern for the extreme rock crawler or 4X4 desert/dune jumpers than it would be for the guy rebuilding a truck to pull his boat/5th wheel or haul a load of lumber or occasional 1/2 yard of sand/gravel all the while traveling on municipal roadways. A manufacturer doesn't know what the application intent will be - while we do know what we plan to do with our trucks, and as long as we don't push them to try to do what they aren't able to do, bolting one together would be fine. I suppose if I was to bolt together a truck, I'd keep an eye on the attaching bolts, inspecting them annually or at least after every heavy load hauled. If, in time, I decided to sell it, I would make sure I point out this issue to a potential buyer.....just as I would any other changes or modifications made to the truck.
BarnieTrk

 

The frame on a slick will flex unloaded. Just look at turning in to a building that has sidewalks and paving six inches higher than the road. the front suspension loads and loads the opposite corner in the rear. and the frame flexes a bit. you can clearly see it by looking at the box verses the cab. Flex in the ladder frame and a rigid body is what killed the uni.

I still do not advocate from professional chassis and suspension fabrication standpoint that bolting together the complete frame is a safe idea. Components bolted to the frame are OK as the stress is a shared transfer.

I believe the issue is that the poster asked this question once before and was told a few months back by me that it is not a good idea. As he removed all the rivets to clean everything and needs to put it back together. I asked other professionals about this and they also agreed with my opinion. But hey i could be wrong and it could work fine. But engineering tells me that working a bolt with grade eight capacity in that manner will cause it to fail due to flexing stresses that they are not designed to accept.

If one does this, do not go to ace or places like home depot or lowes. Go to a reputable bolt dealer that can provide the mill cert, rockwell temper and pedigree of the bolts, nuts and washers. There are a lot of counterfeit grade eight bolts and hardware out there passing off as kosher.

Garbz

Garbz

 

David provides good advice as usual. I wondered about that fellow taking out all the rivets and removing everything for cleaning the frame. One thing I would add is to check a rivet to see if it is loose and or broken...squirt some light oil on the rivet, smack it with a small hammer and look to see if the oil is knocked away from the head of the rivet. If the oil is knocked away that rivet is loose or worse, broken. I use grade 8 bolts for cross members and for the replacement of broken or loose rivets. I use a flat washer under the head and a lock washer under the nut and a locking nut. So far no problems.

 

I have been told by quite a few different people around my area that have built trucks from the frame up that bolting together my frame would be fine under normal street use. Granite I plan on keeping my truck for a long time so I know what limitations I will be putting it under. I drilled all the holes out to 1/2" and with the majority of the bolted parts going back on there are atleast 2-4 bolts for each bracket, crossmember, etc. With 1/2" size bolts it should be fine under normal street use. You start adding a **** ton of torque or maybe see the strip more than a few times I would reconsider the bolt idea. Just my 2 cents, I wish you the best of luck to whatever you decide. Have fun with it.