An excavator is a large, diesel-powered construction machine made for digging out earth with its bucket to create trenches, holes and foundations. It’s a staple of large construction jobsites.

But don’t let the name "excavator" fool you. By swapping out the bucket for another attachment, this piece of excavation equipment can also drive piles, clear brush, load and dump, grade a jobsite and perform other heavy-duty jobsite tasks.

Typically these machines are tracked, but some models have wheels. In the past, excavators required cables or wire ropes for their digging power; but today they rely on hydraulic systems that make them more mobile and easier to operate.

Hydraulic excavators consist of two main sections, the undercarriage and the house, which sits on a rotating platform. The house includes the cab, the counterweight that offsets the force of the digging, the engine, the boom, the digging arm (aka stick) and the bucket.

The boom extends out from the front of the house and meets the digging arm at an articulated joint. The bucket or other attachment (breaker, auger, grapple, hydraulic hammer, etc.) is fastened to the end of the arm. The operator controls the action of the boom, arm and bucket through two joysticks.

Excavator types

Excavators are designed to handle many different types of jobs and come in a range of sizes. According to the Association of Equipment Manufacturers, there are three main categories:

1. Standard excavators weigh between 22,046 and 200,000-plus pounds. Two examples in this category are the 43,000- to 49,999-pound excavator and 30,000- to 35,000-pound excavator. They are best for bulk earthmoving and heavy lifting applications.
2. Midi excavators weigh between 13,227 and 22,046 pounds. These can be used when a jobsite is in a confined area but the work requires something more powerful than a mini-excavator.
3. Mini-excavators weigh less than 13,227 pounds. These versatile machines have a small footprint, making them ideal for activities such as digging trenches, removing stumps and minor demolition projects when jobsite space is tight.

Choosing an excavator

Contractors should consider several factors, in addition to size, when choosing an excavator for their projects.

1. What is the required dig depth? In other words, how far down must the bucket be able to reach into the earth?
2. What dump height do you need? How far will the boom, arm and bucket need to extend upward and outward to put material where you want it?
3. What bucket capacity do you need? The larger the capacity, the faster a job will go, but if precise work is required, a smaller bucket will provide more control.