MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.

Download Now

Report as inappropriate

Atmega pins can source (provide positive current) or sink (provide negative current) up to 40 mA (milliamps) of current to other devices. Also they provide only 5V.

A stepper motor driver like the A4983 provides up to 1A (without a heat sink) or up to 2A (with heat sink) @ up to 35V.

At least you won't get much torque (if any) out of your steppers when driving them directly from the Arduino pins.
I would be more concerned about the possibility to burn out th
e ATMega chip when driving inductive loads like a stepper motor coil directly on the pins. But I'm no expert with this...