another riveting question

[larry harding]

i/m putting a front cross member in my frame. heated the rivets, used a buck and the forming tool in a pneumatic rivet gun. i'm satisfied with the eight round head rivets i installed. my puzzle is how do you do the six flathead rivets on the top of the frame? i tried bucking the flathead part and using the tool under the top flange, all i did was bend the rivet. suggestions please. i looked in the archives a bit but couldn't find any specifics on doing these.

[mcgarrett]

I'm not sure about the specific rivets you're referring to on the Model A, but my Dad worked at the Dallas Ford assembly plant for 32 years starting in 1948 and I remember him telling me about some of the manufacturing processes and he once told me there were some assemblies where they set the rivets COLD! Obviously, special tools involved.

[Neil Wilson]

I used roundhead rivets inserted from the bottom.
After riveting into the Flathead hole of the frame I ground the rivets flat.
I don't have the capacity to rivet inside of the frame.

[Oldbluoval]

I made a buck with an angle. It sits atop a piece of heavy angle iron and slides up under.
Not a practical solution for a “one and done”.
Neil’s answer likely the better choice

[Bob Bidonde]

Make the rivets cherry red hot. Neil Wilson mentions the better way to orient the rivets. Make sure the rivets fill the holes as they are loaded in shear.

[rotorwrench]

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This has been a source of contention for some time. The rivet holes in the frame tell the story better than it's been told by some. Those top holes were countersunk on all the frames I've seen. In aviation, 100 degree countersunk rivets are used a lot for flush riveting but they are generally the aluminum AD type rivets that are not practical for any mating of steel parts. The flat head rivets that are sold are not correct for head on top. Perhaps head on bottom but a round head can work that way too. Ford may have used some countersunk rivets but I've never seen any. This leads to the hot riveting method mentioned by Neil in post #3 as the only viable alternative. There could be problems with this type of riveting if the original top rail countersinks are worn oversize due to a loose cross member then a person may have to weld the holes up and redrill them. The 100 degree countersinks are available from aircraft tool sources and should be available for 1/4" rivet shanks. These are piloted and would give a more uniform countersink than a 115 degree drill bit would. Good fitting holes are a must in any riveting process. If the buck tail is longer than 1 1/2 the diameter of the shank above the top surface then the rivet tail tries to lay over or club foot and that is not good. The countersinking process can make the top hole larger if it is sunk too deep. This makes it very difficult to get the rivet to compress straight down into the countersink. Sink them just deep enough to get a good flat fill. The rivet needs to be very hot on the initial hammer blows in order for it to quickly compress down. Using a pneumatic air hammer is problematic if it has too short a hammer throw. I use a 5X gun with a flush rivet set on this and sometimes use a large regular hammer to straighten a buck tail that is trying to go off center. If the rivet tail fills the countersink and sets up too high then it can be filed back down to flush. Rivet shavers were used to do this in aircraft production back in the day but they were made to shave aluminum and not steel.

A person needs a buddy on hot riveting to be safe. The extra person can heat the buck tail up and manage the torch during the process. It's a lot safer that way. I've done it by myself but it's not an easy task since the buck tail may need to be heated several times to get it properly set. This is a forging process on the rivet so it will be plenty hard enough after the setting process. Let it cool down on it's own. The frame rails suck the heat right out so they cool quick enough.

[aermotor]

I used a large (don't remember the size) nut coupler and tightened between the bottom flange and the flat head rivet in top flange. 1 1/2 diameter tail, heated the rivet and drove with a 3x rivet gun until set - then ground flat. I think it filled the holes and provided the necessary clinch. One man job.

[rotorwrench]

A person can purchase the rivet jacks from some of the model A parts suppliers, They use a nut coupler with a round head rivet profile machined into the bolt that fits the nut coupler. These could be used with 1/4" round head rivets. Perhaps Ford did use the flat head rivets from the bottom up but none of the frames I've worked on had any of the original rivets left in them. most of them had bolts but the fenders didn't fit well with bolts in there. Flush head 1/4" screws would have been better but the folks doing the shade tree repairs obviously didn't care too much about whether they fit or not.

[jwmckenzie]

I have used flat head rivets with the buck inside the frame. Used a rivet jack (nut coupler) with a bolt screwed into both sides to fill the space between the top and bottom of the channel. Found that after I got the rivet jack installed it was helpful to c-clamp the top and bottom of the frame to make sure the frame was not spread during hammering, prevents the rivet jack from walking off.

Support the bottom on something solid so the whole system is supported. Heat the rivet to cherry red and get after it with a small ball peen hammer. If the rivet is hot enough it doesn't take much. When heating the rivet use a small flame and heat from the frame up to the top of the rivet. It is important to get the rivet to fill the hole not just set on top.

Be careful taking out the rivet jack it will be HOT...

[rotorwrench]

Having bucked a lot of rivets during wreck rebuilds in my early days as an aircraft mechanic. I've found that rivets drive better is they are backed by the largest bucking bar that a person can use directly on the buck tail. If using a jack screw set up, it would still be a good idea to back the bottom of the frame rail up with a big old chunk of iron. This works just like a Q ball in a game of pool. The big bucking bar will still take most of the pounding even with all that stuff in between. The weakest link in always that red hot rivet shank.

The hardest rivet job I've ever done was riveting new wheel quick dismount locating dowel pins in a Harley Davidson rear brake drum. Those things are like driving a bridge rivet due to the large diameter of the shank. They made the wheel hub to slide on to those locating pins so the wheel could be quickly removed and the drum could stay on the bike when changing a tire. For those interested, this temporary link shows what they look like.
https://www.ebay.com/itm/17559806063...iABEgJCqPD_BwE