NEMA 17 Stepper Motor 42BYGH401 2-Phase 1.8° Step Angle 1.2A Rated Current, 4-Wire Bipolar CNC/3D Printer Motor for Linear Motion, Robotics, DIY Automation Projects

The 42BYGH401 is a NEMA 17-size stepper motor designed for repeatable, precise positioning in DIY and light industrial motion systems. As a 2-phase (bipolar) motor with a 1.8° step angle, it provides 200 full steps per revolution, making it a common choice for 3D printer axes, small CNC stages, camera sliders, pick-and-place prototypes, and general automation. The motor shown includes a 4-wire lead, suitable for direct connection to bipolar stepper drivers used with Arduino-compatible controllers, CNC shields, and 3D printer control boards.

This motor is a 2-phase stepper, meaning it contains two separate coils (Phase A and Phase B). A bipolar driver energizes these coils in a controlled sequence to produce rotation. With a 1.8° step angle, each full step advances the shaft by 1/200 of a revolution; when microstepping is enabled (for example 1/16 or 1/32), the driver modulates coil current to create finer angular increments, improving smoothness and reducing resonance. Actual positioning accuracy depends on load, driver quality, current tuning, mechanical backlash, and microstepping linearity.

The label indicates 1.2A rated current. Stepper motors are typically current-driven devices; you do not “apply a fixed voltage” like a DC motor. Instead, you use a chopper (constant-current) stepper driver and set a current limit appropriate for the motor and your cooling conditions. Running above the rated current can overheat the windings and demagnetize the rotor; running below rated current reduces available torque. For best results, provide adequate airflow or heatsinking in enclosed builds and avoid prolonged stall conditions.

• Motor type: Stepper motor, NEMA 17 frame class (42mm square body class)
• Model marking: 42BYGH401
• Step angle: 1.8° per step (200 steps/revolution)
• Phases: 2-phase
• Wiring: 4-wire (bipolar)
• Rated current: 1.2A (as printed on the motor label)
• Rated voltage, coil resistance, inductance, holding torque, shaft diameter/length, body length: varies by motor revision; check datasheet or measure for your batch
• Mounting: Standard NEMA 17 mounting pattern (hole spacing and screw size may vary by manufacturer; verify with your bracket/plate)
• Connector type: Bare leads (as shown); connector style may vary by batch

• 3D printers: X/Y/Z axis motion, extruder feeders (when torque requirements match your design)
• CNC/engraving: small linear stages, belt or lead-screw driven axes
• Robotics: joint actuation, pan/tilt mechanisms, grippers with lead-screw drives
• Automation: valve positioning, indexing tables, feeders, lab equipment prototypes
• DIY projects: camera sliders, turntables, plotters, and precision motion experiments

• Driver required: Use a bipolar stepper driver (A4988/DRV8825/TMC series or equivalent). Do not connect directly to a DC supply.
• Coil pairing: Wire colors are not a guaranteed standard across all batches. Identify coil pairs using a multimeter (two wires that show continuity belong to the same coil). Connect one coil to A+/A- and the other to B+/B- on the driver.
• Current limit: Set the driver current limit to match the motor rating (1.2A per phase) or lower if cooling is limited. Follow your driver’s Vref/current-setting procedure.
• Power supply: Choose supply voltage based on driver and speed requirements; higher voltage (within driver limits) can improve high-speed torque by overcoming coil inductance.
• Mechanical fit: Verify shaft diameter, shaft length, and mounting screw compatibility with your coupler/pulley and bracket before final assembly.

1x NEMA 17 Stepper Motor 42BYGH401 with 4-wire lead