How to Cut Off a Master Lock

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Things You'll Need

  • Dremel hand tool

  • Metal cut-off discs

  • Dremel mandrel

  • Flat-head screwdriver

  • Dremel wrench

  • Vice or clamps

  • Leather glove or oven mitt

  • Safety glasses

If you forget the combination to your Master Lock, you can cut it off quickly.

Master combination locks have a hardened steel shackle that cannot be cut with a standard hacksaw blade. The shackle is hardened steel to deter thieves from breaking it. However, occasionally you might misplace the key for one of these locks or forget the combination, preventing access to your belongings. If you have a Master Lock that is closed and you lost the key or forgot the combination, you can cut it off yourself in just a few minutes with the right tool.


Step 1

Attach the metal cutting disc to the Dremel tool mandrel. The mandrel is a small metal bit with a flat-head screw on the top. Loosen the screw, place the disc horizontally on the top of the mandrel, and replace the screw in the center of the disc. Tighten the screw to the top of the mandrel with a flat-head screwdriver.

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Step 2

Insert the mandrel into the collet on the Dremel. The collet is the small sleeve at the spinning end of the Dremel tool. Press the button on the side of the Dremel to hold the collet in place. Loosen the retaining nut on the top of the collet and slide the mandrel inside the sleeve. Tighten the collet with the wrench that comes with your Dremel tool.


Step 3

Place the Master Lock in a vice or clamp it down in such a way that you don't have to hold it with your hands while cutting. The lock will become very hot. If the lock is attached to something, you may need to have an assistant carefully hold it steady with a leather-gloved hand (or an oven mitt).


Step 4

Put on your safety glasses to protect you from flying sparks. Power on the Dremel tool and slowly cut away at the base of one side of the shackle.

Step 5

Press the cutting disc against the shackle until the Dremel has cut completely through the Master Lock. Allow the tool to do most of the work. Don't press too hard, or the cutting discs will shatter and you will need to replace them. If the cutting wheel becomes too small during the cutting process, replace it with a new one.

Step 6

Turn the shackle sideways once it's been cut. You can now remove the Master Lock.


Always wear eye protection when cutting steel with a Dremel tool.


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