This NEMA 17 Stepper Motor is bipolar, For 3D Printer Robotics 1.8° step angle (200 steps/revolution). Each phase draws 1.7 A at 4 V, allowing for a holding torque of 3.2 kg-cm (44 oz-in).  When used with a unipolar stepper motor driver. We recommend using it as with  DRV8825 or A4988.
This motor Satisfies all your robotic needs with a selection of high quality & diverse stepper motors DRV8825 or A4988. These simple but very powerful motors deliver smooth motion and nice holding torque.
Our 5x8 coupler can be used to mount objects on the stepper motor’s 5 mm-diameter output shaft, and our NEMA 17 aluminum bracket offers a variety of options for mounting this stepper motor in your project. A similar NEMA17 stepper motor is available with the different specification that enables you a wide range of stepper motors from hallroad.org

Specifications:

• Size: 42.3 mm square × 50 mm, not including the shaft (NEMA 17)
• Weight: 350 g (13 oz)
• Shaft diameter: 5 mm Round
• Steps per revolution: 200
• Current rating: 1.7 A per coil
• Voltage rating: 4 V
• Resistance: 1.6Ω per coil
• Holding torque: 3.2 kg-cm (44 oz-in)
• Lead length: 4cm
• Output shaft supported by two ball bearings (internally).

The datasheet is not available for the exact part but here is a similar one which is 95% compatible with this motor. datasheet.

Dimensions

The following diagram shows the stepper motor dimensions in mm. The dimension labeled “length” is 50 mm. The output shaft has a 5 mm diameter.

The inside of a bipolar stepper motor (SOYO NEMA 14-size).

Stepper Motor Applications

Stepper motors are generally used in a variety of applications where precise position control is desirable and the cost or complexity of a feedback control system is unwarranted. Here are a few applications where stepper motors are often found:

• Printers
• CNC machines
• 3D printer/prototyping machines (e.g. RepRap)
• Laser cutters
• Pick and place machines
• Linear actuators
• Hard drives