Hi everyone, only my third or fourth post. I've been using alot of the advice on my '53 F100 restore/mod..
I have a question about the crossmembers. I've been working the frame (wire wheeling), and what have you guys done about the crossmembers? There is rust between the top of the crossmember and the top part of the frame. Can't get at it to clean. My reaction is drill out the old rivets and replace with grade 8 bolts and nuts. Is this what everyone else has done? Or is there some sort of 'magic' rust remover that I can trust will remove it all...
Thanks for the input..
Glenn

 

On mine I just used a wire brush in those areas, applied a rust remover/metal conditioner and then painted it as best as possible with POR-15 since the rust was not that bad. You can remove the rivets and replace them with bolts if you're a perfectionist and feel it's absolutely necessary to get in there, but it seems like a lot of unnecessary work to me.

 

I honestly can't remember if it was on here, the HAMB, or MSN Flathead site, but there was an exhaustive discussion of bolts to replace rivets somewhere about 3 - 4 yrs ago. There were people who knew their stuff weighing in with hard data, so I would do a websearch.

The thumbnail summary of it was: 1) rivets and bolts are not equivalent methods to hold pieces of a frame together 2) structural bolts have different properties than machine bolts, so Gr. 8 is not necessarily the bolt to use 3) lots of people have drilled out rivets and gone back with Gr. 8 bolts, and their cars/trucks are still together 4) rivets are available from a number of sources 5) do not under any circumstances try to weld the frame back together.

Other factors: the frames on most early iron (pre-IFS) were designed to flex extensively, which rivets can accomodate, but bolts are less able to do. Upsizing a little when going back with bolts is a good plan. Several factory service bulletins describe replacement of rivets with bolts, so it appears to have been considered in the design of some frame elements.

Personally, if you can see flaking rust in the area you describe, I'd want to drill and repair. I have a thing about structural strength.

 

I've done removal and re-install with good hardware AND a short Mig weld bead. And, I've drooled in some liquid rust converter in some areas as well. I trust the rust treatment because it chemically converts the oxidation. If it is in a place that would be a long and involved process to do fix it again one day, you might want to do it completely now. The fix will never be easier than it is right now. Grade 8 is the way to go. You hear stuff about the flex ability of Grade 5 and the brittleness of Grade 8 but truth be told, the Grade 5 would be dead and gone from shear and bend before the Grade 8 would let go.

 

Ross, I'm in comp-lete agreement with you that the arguments are all over the place--with solid argument both sides. My trial and error is only mine so its really a personal thing. It comes down to what one personally trusts. I suppose there are anumber of wrong ways to do it but there are a number of right answers as well.

 

Found it---Rockcrawler dot..... will have a tech article called "Making the Grade-A technical discussion-Grade 5 vs. Grade 8 by David M. Potter." Its worth reading as another viewpoint.

 

I am an aerospace MRB Engineer. My job is to design repairs for aircraft structures that have defects during buildup. These structures tend to be much more delicate than truck frames and use exotic materials and fabrication methods. They are also designed with smaller structural margins of safety.

I know from my training that there is little inherent difference between a rivet and a bolt in structural applications. In most cases, it is the joined materials that will fail way before the fastener breaks. A grade 5 bolt is stronger material than the mild steel rivet it replaces. Grade 8 is stronger still. So, using either grade 5 or 8 bolts will be a stronger attachment than the rivet they replace.

The only caveat to this is where the bolt is significantly smaller than the hole. A rivet fills the hole completely when squeezed. A bolt slips thru the hole and has some clearance. If there is a lot of clearance between the bolt and hole, and the bolt is not torqued sufficiently, the joined members can move under load relative to each other and fret (wear) the bolt, causing it to fail prematurely at some later time.

The bottom line is: drill out the rivet hole to a matched size that is 1/64th larger than the bolt and torque the bolt up well using flat and lock washers. It will live longer than the metal it joins.

Now you know why nobody asks any particulars about an engineer's job and why we tend to be boring at parties.

Now, back to our regular program....

 

Thanks guys! I really appreciate all the info, I'm going to check out that web-site tech article on the grade 5 vs. grade 8. After reviewing the all the posts and knowing that my frame is not "rusted real bad", just some surface stuff, I might just try and get most of it with a wire brush, and then brush in some rust converter. I do have some rivets that have corroded away, the tails anyway. And those I will have to replace...
Thanks again!
Glenn

 

In working on heavy duty trucks, I have run across frame bolts. These have a shank that is slightly larger than the threads and is a .002-.003 press fit into the hole in the frame. Most of the ones I run across are 5/8" - 1" dia. so I don't know if they are offered in smaller sizes. These would be a good replacement for frame rivets.

 

Since we are on the sudject of bolts i could use some info myself. My running board brackets have fine threaded square nuts weled to them and i wanted to cut these off and replace them with a standard thread stainless bolt and a nylok nut. Can anyone tell me if this is a good ideal or not. The reason for the s/s is because well, they look good and also because i can get them for free.

 

Randy,
I couldn't have said it better myself. My wife complains all the time that I'm boring. She never wants to watch "Modern Marvels" on the History Channel. And my daughter said she would never date an engineer because her father and brother are both engineers. Her current boyfriend and the previous two ...engineers.

Phil

 

I always wanted to be an engineer...especially, since I like blowing the horn at crossings...