It may be possible for a layperson to extract a broken key from a keyhole. However, that extraction process is fraught with risks that can worsen the situation. This article discusses some of the common mistakes that often push the broken segment deeper into the lock or that affect the lock mechanism.
Using Liquid Lubricants
You may have heard that spraying a lubricant into a lock may make it easier for you to remove the piece of broken key that is stuck inside that lock. However, not all types of lubricants are suitable for this task. Liquid lubricants are an example of lubricants that you should never use when your key breaks inside the lock. These oil-based lubricants can gum up the internal components of the lock. That lock may later fail. It is better to use dry lubricants, such as graphite sprays, when you want to remove a broken key. Just make sure that the powder doesn't stain any surfaces near the lock.
Inserting the Remaining Segment
Do not try to insert the free fragment of the key into the keyhole in order to open the lock. That action will force the broken segment to move deeper into the lock. It will then become very difficult for you or a locksmith to extract that stuck segment. It is also unwise to discard the segment of the key that remains outside the lock. That piece will be needed by the locksmith when it is time to cut another key for the lock after the broken piece has been retrieved. It may become harder for the new key to be made if there is no impression of the old one because you discarded the remaining piece.
Not Evaluating Tools
A lot of information is available on the different improvised tools, such as tweezers and paper clips, which someone can use to extract a broken key from a keyhole. However, each of those tools may be suited to a different set of circumstances. For example, some tweezers may be so thick that they will end up forcing the broken key deeper into the lock. Similarly, super glue may be inappropriate if you cannot see any section of the stuck key. Think carefully about the suitability of any makeshift tool/material that you would like to use to extract a broken key so that you don't use a tool that will worsen the problem.
Breaking your key inside a lock as you try to get into your home can be a very stressful experience. It is therefore advisable for you to call an emergency locksmith for assistance.