Rolled angle rings are commonly used as angle flanges to connect cylinders or pipe. Welded to the pipe or cylinder, the mating angle rings are commonly bolted together through holes put in the horizontal leg of a leg-out angle ring. (Leg-out angle rings look something like a old timey straw hat without the top. The brim would be comparable to the horizontal leg of a leg-out angle ring.)
Bolt holes can be put in the horizontal leg, the vertical leg or both legs. In the case of the horizontal leg, the following specifications are needed: number of holes, hole size, hole spacing, and bolt circle (the distance from the center of the holes to the center of the ring.) In the case of the vertical leg, the following specifications are needed: number of holes, hole size, hole spacing, and gauge line (the distance from the apex of the angle to the center of the hole.)
Holes can be punched singly after being manually laid out on a ring. This method could be used to put holes in large segments several of which might make up, say, a single 60 foot diameter ring. Smaller full rings can be punched with automatic punching machines.
Depending on the application, bolt holes might be punched or drilled. Punched holes are usually slightly larger than the bolt, e.g. a 7/16 inch hole diameter would be provided for a 3/8 inch bolt. If more precision is required, bolt holes may be drilled rather than punched. If the hole is to be tapped, then the hole will be punched or drilled undersized. In addition to round holes, slots can be punched or even plasma or laser cut.
Countless variations of the above alternatives can be provided:
Orientation: angles can be rolled leg-in, leg-out, off axis as well as to multiple radii and into compound bends—and all with bolt holes.
Hole size: even in a single ring, different hole diameters can be provided. 1/32 inch diameter holes can be drilled. 1-1/2 inch diameter holes can be punched. 4 inch and larger holes can be drilled.
Hole spacing: holes can be equally spaced or irregularly spaced.
In addition to functioning as mating flanges, rolled angle rings with bolt holes can be fastened to machinery and equipment including, among many other applications, blowers, tanks, trucks, antennas and rail cars