Patterns: We create paper patterns for our hinges that look like this:
They can be traced and then glued onto metal sheet and trials made until a final master is made which can be photocopied and copies pasted on metal and cut out or laser cut (we use Laser Precision Cutting). For this small hinge we used 18 gauge mild steel. The pin was made from a 16 penny box nail. We glued the pattern on the stock (rubber cement works fine), center punched for the screw holes and then cut out the hinge piece using an Edwards #1 shear, hacksaw and cold chisel. We cut the basic outline with the shear, then cut the barrel(s) with the hacksaw (make your cut on the waste side of the line). A cold chisel cut the waste piece between the two barrels after hacksaw cuts had been made.
Die:
The die is easy to make, but isn’t necessary if you are only doing a few hinges. You can fairly easily roll the barrels hot around a pin mandrel, even for very small hinges. We use 01 tool steel for our dies, though you could use mild steel (A36) with a Super Quench heat treating. A block of metal large enough for the die is found. A hole with a diameter (slightly larger than the pin thickness and 2 X stock thickness) that will allow the material to roll and not be too tight or too sloppy is drilled. Two hacksaw cuts are made down to the hole (we use two blades in the hacksaw cutting at the same time for a nice, narrow slot). The hole and slot are cleaned up with files (chainsaw files have little taper for the round hole) and we further polish the die with Clover Compound. If you are going to pound the material through the die rather than using a press you need to make a pusher so the hinge edge isn’t marred.
File Tip: For the bulk of filing hinges we use two files, both with safe edges. We use a square bastard file (6 or 8 inches long) that has had one side ground smooth. We use a fine flat file (6 inches long) that has a safe edge or has one edge ground smooth. The safe edge is used against the surface that is not to have material removed, generally the barrel for the square file and the bevel for the flat.
Pins: For smaller hinges we use nails for pin stock, generally 16 penny box or common. The pins are cut to size (slightly longer than hinge barrel) after the ends are chamfered (cut off the pointed nail end first). We use a hinge pin tool (made of a piece of bar stock) for heading small pins that has a hole drilled slightly larger than the pin diameter and just the right length for the hinge barrel. A pin that has been heated (but still at a black heat for small pins) is placed into the tool chamfered end first and headed with a ball peen hammer. The pin is then knocked out of the tool.
There are a number of other ways to head the pin (while hot in the hinge, for example), and tools to hold pins while heading.
Beginning the Hinge We make several sizes of hinges in the butterfly or dovetail style. These are cut for us out of mild steel plate (16 gauge) by a company with a laser. We originally cut these ourselves by hand with a shear and hacksaw but found that the laser cut hinge parts were more precise and allowed quicker fitting.
The Blank This is a laser cut blank with the center punched marks for the holes already made. The laser cutting has both pieces held together by a thin sliver of steel. After punching, we break the two pieces apart.
Punching the Holes We use a large "hand punch" to punch out the holes in the mild steel.
Molly and the Punch The punch that Molly is using is a Whitney number 8. This punch is capable of punching a 1/4" hole through a piece of 1/4" thick mild steel. It is held in the vise while Molly is using it. A punch goes just below the cam in the top, and a die is held at the bottom. We have a number of different punches and dies.
Starting the Eye The hinge part is heated in the forge and then moved quickly to a swage block where the curve for the start of the eye is formed using a small hammer peen. The metal because it is so light cools very quickly while working.
Starting the Eye Here is a hinge half with a started eye.
Rolling the Eye
The eye of the hinge is rolled using a special die and a press, in this case a fly press.
Rolling the Eye The pieces with started eyes are on the left, the rolled eye pieces are on the right. The yellow cup holds oil which lubricates the pieces before they are rolled in the press.
Hinge Eye Die This is the die we use for rolling hinge eyes. The piece is placed in the die, a brass piece in the front keeps the hinge from scraping against the die while being rolled. The pin that the eye is being rolled around goes through the die. The die is made of tool steel because it must be tough to resist wear.
Placing Die in Press The die with its hinge piece is placed in the fly press under the ram.
Rolling the Eye Once the die is under the ram, Molly swings the cross bar and the press screw forces the hinge piece through the tool. Notice the counter weights on the cross bar.
Removing the Pin After rolling the eye, Molly drives the hinge piece out of the die with a hammer and then pulls the pin out of the die piece using a pair of pliers. It is a tight fit.
Assembling the Hinge The hinge parts are filed and assembled at a special bench.
Molly at the Bench This is a bench we use for assembling hinges. It has a special vise for holding the hinge parts, a steel block, and space to hold tools and unassembled and assembled hinge parts.
Filing the Bevel A bevel has to be filed so that the hinge parts open and close smoothly when they are assembled.
Filing the Barrel The edges of the barrel need to be filed so that the hinge parts fit together nicely.
Fitting the Parts Each hinge half is fit with the other half. A close fit is required so the hinge will work properly.
Driving in the Pin A hinge pin is then driven into the assembled hinge halves.
Beginning the forging We forged the assembled hinges to put a chamfer on all the edges and to make the hinge lie flat.
Forging the Chamfers The chamfers are forged using a small hammer. Since the stock cools so quickly it takes two heats to do this.
Heating the Hinge The hinge is pulled quickly out of the fire, transferred from the special tongs to a pair of pliers and the second heat is taken to forge the chamfers.
Working the Joint While the hinge is still hot, the joint is worked back and forth. The hinge will then be taken to a steel block to be flattened.
Wire Wheeling the Hinge The hinge blank, after cooling, is tested to make sure it operates correctly, and that it lies flat. Then, it is placed under a treadle wire wheel to remove loose scale. Usually it takes several heats to get the hinge properly flat and with a good layer of scale to hold the finish.
Finishing the Hinge When the hinge is ready, a hot finish of beeswax and raw linseed oil is used. The hinge is examined when cool and sometimes has to be reheated, wire wheeled and refinished if there are scale “pops.� The scale is what gives the hinge its black finish when the oil and wax are applied. If scale is popped, that area will show as a shiny silver spot.
Pre-Heating the Hinge The hinge is heated slightly so that the finish will cover every part.
Hinge in Finish The raw linseed oil and beeswax mixture forms a paste when cool. The hot hinge will sink into this paste and become covered.
Warming the Finished Hinge Again After being dipped in the finish, the hinge is again held over the fire so that the hot finish will reach every pore of metal.
Cooling the Hinge The hinge is laid onto a large steel “bowl� to cool. When cool enough to touch the extra finish is wiped off. After two days the hinge receives its final hand waxing with Johnson's Paste Wax.
Finished Hinges Here are three different sizes of butterfly hinges
Fuente http://members.citynet.net/sootypaws/Blacksmithing/hinge/hinge_bsnotes1.html