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Home > Bump Key Info

Bump Key Info

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To fully understand how a bump key operates, we must first
understand how a common lock operates.

The cylinder lock is the most common type of lock in use today. Most cylinder locks use a pin and tumbler system which is comprised of upper and lower pins of varying length, along with small springs. Lock bumping works in the same manner as lock picking, whereas the pins within the cylinder (or plug) must be moved into the proper position to allow the lock to open.
Whether lock picking or lock bumping, the techniques are similar. To bump a lock, start by choosing the correct key for the lock set. Compare the key way shape to that of the lock, they should match. Insert the chosen key, and if it goes into the lock fairly easily, you most likely have the proper bump key. Insert the key all the way into the lock, then pull it back out one notch (or click). Apply slight turning pressure on the head of the bump key in the direction that opens the lock - NOTE - you will have to adjust the pressure for different locks, usually no more tension than what it takes to turn a regular key. Find an item to use as a bump hammer, this could range from a plastic serving spoon, to the handle of a screwdriver. Give the bump key a slight tap with your "hammer"; you will need to adjust your amount of striking force, and striking angle until you find your "groove". If the lock does not open, try again, and try different techniques. Bump keys do work once you get the feel for them, but they are not magic!

This view shows how the pin and tumbler system works within a cylinder lock. The small springs near the top keep constant downward pressure against the pins. Note how the upper pins are within the shear line area, this is what "locks" the lock. The plug cannot turn when these pins are within the shear line.
The top and bottom pins must be separated, allowing the top pins to "rest" upon the edge of the plug.

A standard key uses a series of ridges to align the pins into their proper position. When properly aligned, the upper pins will rest just above the shear line, while the lower pins remain within the plug. The cylinder can now turn freely with no obstructions.
Lock manufacturers assign key codes to both key blanks and locks. These key codes refer to what depth the key blank should be machined, and to what size pins should be used within the lock set.

Bump keys are made by machining a key blank to the lowest factory setting (key code). Notice how all the peaks on the key blank are of the same height. Once you have selected the correct bump key for the lock, insert the key entirely except for the last notch. This is commonly referred to as the "pull back method
"; whereas the key is fully inserted into the lock, and then pulled back one notch.

Once the bump key is positioned, slight rotational pressure is applied to the head of the key. The key is then "bumped" into the cylinder. The teeth of the bump key produce a slight impact against the bottom pins. The lower pins then transfer this energy into the upper pins, causing them to rise above the cylinder and the shear line. The separation of top and bottom pins is very brief, but in this moment the lock cylinder is easily turned.

Now that's how you bump a lock!