Like HowStuffWorks on Facebook!

How Jackhammers Work

Percussive Power

Jackhammers are a type of percussive drill. They pound away at a surface to break it into smaller pieces. The mass of the tool itself, along with gravity, are two main elements that make jackhammers work because they help weigh down the machine and keep it in contact with the target.

As the bit impacts the rock at between 1,000 and 4,500 hits per minute, it immediately stresses the surface and causes the formation of irregular fragments. The bit pulverizes these fragments into a fine powder or granules that tend to pool around the tip of the bit.

Although these powdery remains absorb some of the bit's energy, they also transfer that energy to surrounding rock. Larger cracks form as the bit pounds the rock. Typically, those cracks stabilize as the bit hits its maximum reach.

As the bit retracts, it pulls along many of the rock chips, leaving behind a small crater. In some jackhammers, a valve opens and flushes the crater with a blast of air or water to clear the hole of debris.

Then, the operator moves the tool back a few inches and triggers the jackhammer again, restarting the process and propagating the initial smaller cracks into larger ones. Larger, deeper fractures in the rock join together, causing the breakage of large pieces that workers remove with other tools or larger machines.

It's important to clear craters as the job progresses. Otherwise the jackhammer might continue shattering chunks into smaller and smaller pieces that get in the way.

There are several types of bits for different jobs. For basic breaking purposes you'd chose a point bit, which, as its name implies, is simply a pointy shard of metal. To create a cleaner edge and provide better control of cracking direction, you might want a flat bit. These can be either narrow or wide depending on the job. Wider bits don't penetrate very quickly, so using them often takes longer.

Regardless of the style, it's vital to avoid going too deep into the rock. It's extremely easy to get the bit stuck, meaning you'll be taking an unscheduled break until you figure out how to loosen it.

Sharp bits are critical for maximum efficiency. When bits become dull, both the man and the machine have to work much harder to crush and crack the rock. That means you should sharpen the bit regularly, and the harder the rock, the more often you should check the bit.

Most jackhammers are used to work straight down or on an incline. It's possible to hammer horizontally, but because of the tool's immense weight, this task requires two people, or better yet, a jackhammer stand that supports the heft without human help. Overhead hammering requires smaller jackhammers or machine assistance.