On 1/12/07, Jim Beacon <jim at g1jbg.co.uk> wrote: The technique for driven rivets is to deform the diameter of the rivet so that it expands within the holes to lock the parts to the rivet shank, and then form the "Shop head" to squeeze the parts together. In Aircraft for regular rivets, this is done with a rivet set that is either driven with a shop hammer or with a pneumatic hammer. The rivet set is made of tool steel, usually a few inches long and 2 or 3 times the diameter of the rivet. It has a polished depression that conforms to the shape of the factory head. A bucking bar is held against the blunt end of the rivet and a few strokes are made to the rivet set, then the shop head is inspected by eye or with a gauge to determine if the proper amount of deformation has occurred. The skill is in sensing how many hits with the hammer it takes to make a perfect head. When the distance between the buck and the set are too great a second person is needed, for instance the fuselage tail cone section usually needs someone thats able to fit in the tight space making for interesting stories. Rivets that don't meet the spec have to be drilled and then punched out and replaced. There are special rivets with a larger shank but same size head incase the hole becomes deformed in the process of removing the faulty rivet. Flush rivets were introduced with astounding results for aircraft by Howard Hughes with his R1 racer. The hole is drilled with a countersink area to hold the factory head, and the set is a mushroom shaped polished tool steel tool. Rivet squeezers can be hand held or mounted on a fixture and are used where they can reach both sides to speed up production as they set one or more rivets in one measured motion. The rivet length before driving is usually 1.5 times the diameter. Blind rivets are used where its not possible to place a buck to drive the rivet. The "nail head" pulls thru the hollow rivet to expand it to fit the hole and to create a shop head. Pop Rivets are a popular for light duty and consumer use. There are much tougher and expensive blind rivets such as the Cherry Max brand are used in structural and aircraft work. Jay, loose rivets can sometimes be tightened by placing a buck (1lb chunk of steel, hammer, dolly, etc) on one side, and tapping the other with the proper set, or in a pinch a hammer. This works for some but not all depending on size and alloy but its worth a try if you can get to both sides. Books have been written on this, and there are also videos, and classes if one is interested in learning more. And of course I probably left something out or mixed something up so before you go out and rivet something you should consult something more reliable.