Handcuffs are common restraint devices often used by law enforcement that lock people's hands or feet together to reduce mobility. Handcuffs are also available commercially for private use, and can cause serious problems if a person or child is locked in them and the keys are missing. Handcuffs are commonly constructed of steel with chrome or nickel plating, so any steel-cutting tools can cut handcuffs.
Bolt cutters can safely and quickly cut through steel using a large amount of force generated by the tool's two arms that is concentrated on the cutter's sharp blades. Ensure when you select a bolt cutter you pick one that is capable of cutting steel and always wear safety glasses while using this tool. The person who is handcuffed cannot use this tool on themselves, but the bolt cutter can safely be used to remove the wrist cuffs.
Hacksaws are small hand-held saws that can be used to cut the chain between the two wrist cuffs, but should not be used close to the skin to cut off the wrist cuffs themselves. Select a hacksaw that is capable of cutting steel, and hold the chain taut over a sturdy wooden work bench while a second person saws. Always wear safety goggles while cutting metal. This method could generate heat due to the friction that could burn the cuffed person, so use extra caution.
A drill press is a heavy duty drill mounted to a table that could be used to cut the chain between the two wrist cuffs. This tool is not safe for cutting the wrist cuffs. Select a drill bit that can cut steel, and carefully position it over one loop of the chain before drilling, and always wear safety goggles while cutting metal. After cutting through the loop, remove it from the cuffs to free the person's wrists or ankles. The person who is handcuffed cannot operate this tool themselves.
If someone is accidentally trapped in a set of handcuffs and none of these tools are available, call the handcuff manufacturer, a locksmith or local law enforcement for assistance. There may be other options or safety mechanisms available for your particular model of handcuffs that you do not know about.