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First off I know the subject of rivets has been discussed on the forum but
what is the correct way to set a rivet on a C2? There is conflicting information on the forum. Two knowledgeable people; John Z states to place the buck on the rivet head and use the gun on the tail. John McGraw states to place the buck on the tail and use the gun on the head. Also if I were to buy a used rivet gun should I buy 1x, 2x, 3x or 4x as the rivet used on our cars should be made from 1100 alloy, which is nearly all aluminum and not treated. I'm not looking to stir up a hornets nest or throw bricks on this subject.
I used John's method when restoring my old '69. Buck on head and gun on tail. I practiced a bunch on scraps to get the technique down before riveting anything on the actual car.
Which end to buck? Peen down the tail if there is metal around it. Examples: tire tub lid Y-strap, wire hooks, underbody reinforcements.
Bucking bar goes on the head when it rests on fiberglass. Setting the head would crush the polyester/glass matrix.
The aircraft guys have metal on both sides and do buck the tail, while gunning the head with a flat rivet set bit. At least that's what I came up with when asking the same questions as you are.
I work in the aircraft industry and have for over 45 years. It's rare to buck the rivet from the head. You always have a rivet die with a concave shape that fits over the head and buck the tail of the rivet. Of course this is for aircraft. Rivets actually don't care how they are driven (or flattened), the issue is crushing the head beyond an acceptable tolerance.
John McGraw's method of hammering from the head using a bucking bar with the correct concave shape works best IMHO. Here's why. When you hammer from the tail end, no matter how hard you (or a helper) pushes on the head end with a bucking bar, the hammer is ALWAYS trying to push the rivet stem back out of the hole. Plain and simple.
When you hammer from the head end (I have 2 sizes of flat + concave stems for my hammer gun depending on the shape of the head ... most are flat), the hammering action is always keeping the rivet seated against the fiberglass and a properly shaped buck bar on the stem will create a nice rounded end while pulling the metal piece up tight to the other side of the fiberglass and properly expanding the rivet to "fill the hole".
I've done them both ways and both work. But I find hammering from the stem end quite often leaves the metal piece not quite snug against the fiberglass, which usually results in me cutting the rivet off again and doing it right.
Mike Geary mentioned hammering from the head end "would crush the polyester/glass matrix". That is correct IF you fail to turn down the hammer gun to no more than 30# psi. So you need to regulate the air flow to the gun to hammer from the head end but in my experience you will have better luck getting a nice tight fit up against the fiberglass.
Hey Mike, I agree that's how the assembly line likely did it ... at least on the tire tubs, and probably lots more parts. Sure made a crappy job out of those rivets didn't they.
I prefer to deviate from the practice of the day 50 years ago and make them look nicer ... and secure the part more solidly, but that's just me. And I would probably lose points because of it at a Top Flight event! Bill
BTW Mike, that tub is soooo clean it looks brand new. If the rest of the underside of your car looks like that ... that is impressive. A "brand new" 52 year old car. Bill
I have done it both ways. Suggest you practice a bit both ways, read the comments above, and then make your choice.
Suggest a 3X gun, but as Mike G says, a 2X will also do. Each "X" represents 1/16 inch rivet size. i.e. 3x = 3/16.
I have a used CP gun and like it. IR is also good, as are a few other major brands. Check Ebay and also a few rivet suppliers that also sell new and used guns. Make sure your compressor has a good regulator to set your gun at needed pressure. You don't need a lot on these fiberglass cars with aluminum rivets.
The mass of the buck definitely plays a role in doing this job.
The shop I use has a 3"X6"x1.5" thick block of brass that we use to "buck" the rivets. Typically we buck the head and drive the stem of the rivet with the air tool. Despite what you might think, when held firmly against the head of the rivet, the mass of the buck resists movement enough that the tool does it's job on the shaft of the rivet without pushing it out of the material. When done properly I've never found a gap between the material. In some places, we use a short length of brass rod between the head of the rivet and the block of brass when the "buck" can not be placed directly on the head of the rivet.
The air pressure driving the tool is also critical. Too much pressure will smash the rivet and make controlling the tool difficult. Too little pressure will place more force on the material and not take advantage of the mass of the buck. Typical pressure should be around 25 psi, but with practice you will find what works best for you.
There are a few locations on the C2 however that do not allow room for the tool (to operate) and it may be necessary to drive the rivet into the buck.
For a "riveting" experience, check out Champaign Lady, the B-17 bomber rebuild. I noticed that they put green painters tape on both the set and rivet head. This does help keep the set on the rivet and prevent the set from walking. My guess 99.9999999% of the rivets on that B-17 are replaced. If you are into structures check out the aft spar attach repair, Boeing approved.
The rivets we use are soft aluminum. IF the shank is to long they will bend over like nails when you shoot them. Rivet guns and air hammers are two different animals. I use an E3 gun low press. 1 to 1 1/4 shank exposed before bucking.
Brgds,
Rene
Rivet setting?
