Antique keys are an easily collected item and are often found in antique stores, thrift shops and at garage sales. Some antique keys are similar, and others are different sizes. Some antique keys are made to go with an antique lock within a vintage-era home, or some people simply like the look of an antique key on their keychain. Copies of antique keys are needed when an antique key is used on a daily basis for a lock. If an antique key is lost, it is always a good idea to make a few copies of the key to have handy.
Make a bump key. Any key can replace an antique key needed to open an old lock in case of an emergency, or to have extra spare bump keys if the antique key is ever permanently lost. Take any modern key, and a black Sharpie pen, and make a mark below the ledge of the key. The ledge of the key is the bottom straight line across the key, where the indentation is.
Use and inexpensive triangular shaped metal file from a hardware store, and file the metal on the key all the way down to the lowest edge. File away the 5 teeth of the key--the little triangle edges--to get to the bottom ledge. Test the key in an antique lock by tapping the key into the lock to open it. The key should be able to get the door open, and can be a substitute for a lost key. Some bump keys are like antique skeleton keys, and can work in most locks, not just antique locks meant for antique keys.
Press the antique key into a key mold kit; one containing Blu-tak or clay. Take the mold to a locksmith who specializes in replicating antique keys. Sometimes the antique key is made from old metal, or is a barrel key, with a hollow interior.
Don't try to copy more intricate barrel antique keys, because these need to be specially made. Take these types of antique keys to a locksmith or experienced key maker, and have the key made from the impression you took with the mold, or if need be, take the original key in with you for him to copy.
Go to a local hardware store, and use the key making machine to make a duplicate key. Follow instructions posted on the machine or ask a worker in the hardware store for help.