Understanding the Creality 42-40 Stepper Motor Datasheet

The “42-40” is the stepper motor Creality reaches for more than any other. The name is a size code, not a model mystery: a 42 mm square mounting face (the NEMA 17 standard) and a 40 mm long body. On Creality machines it is best known as the extruder motor, and it also drives axes on parts of the CR-10 family. This page is the motor’s datasheet translated into plain terms — what each value means, how the wiring works, and what to check when one misbehaves.

Creality 42-40 datasheet

Parameter	Creality 42-40
Motor type	2-phase hybrid bipolar stepper, NEMA 17 frame
Body size	42 × 42 × 40 mm
Step angle	1.8° — 200 full steps per revolution
Rated current	1.0 A per phase
Holding torque	0.4 N·m (40 Ncm)
Shaft	5 mm diameter, D-shaped (flat), about 21 mm long
Leads	4 wires (two coils), JST-style connector at the motor
Weight	About 290 g

Two of those numbers do most of the practical work. The 1.8° step angle is why Creality firmware steps-per-mm values look the way they do: 200 full steps per turn, multiplied by the driver’s microstepping, divided by how far one turn moves the axis. And the 1.0 A rating is a ceiling, not a target — drivers are normally set below it, because a stepper run at full rated current for hours gets hot enough to soften the plastic mount it is bolted to (a real consideration on an extruder, where the motor sits against printed or injection-moulded parts and a heat-soaked motor can also warm the filament path).

Where the 42-40 is used — and its two siblings

Creality’s motor family is a size ladder, and the sizes are not interchangeable without thought:

• 42-34 — the shorter sibling (34 mm body, less torque). The axis motors on the Ender 3 generation are typically this size.
• 42-40 — this motor. Per Creality’s own documentation, it is the main extruder (E-axis) motor on the Ender-3 and Ender-5 series, and serves X/Y/E duty on the CR-10 series. Extrusion is the demanding job here — pushing filament against nozzle back-pressure is continuous torque work, which is why the extruder gets the bigger motor.
• 42-48 — the longer, stronger sibling (48 mm body), fitted where loads are bigger — for example the Y axis and extruders of large machines such as the Ender 5 Plus and K1 Max class.

That is also why “my replacement NEMA 17 doesn’t feel as strong” happens: a generic 34 mm motor bolted onto an extruder is a downgrade in holding torque, even though it fits the same holes and spins the same way.

Wiring: two coils, four wires

The 42-40 is a bipolar motor: inside are two separate coils, and the four leads are the two ends of each coil. The driver energises the coils in sequence to walk the rotor around. Practical consequences:

• Finding the pairs: with the motor unplugged, a multimeter on continuity/resistance shows a few ohms across each coil’s two wires and open circuit between wires of different coils. Shorting one coil’s wires together (motor unplugged) also makes the shaft noticeably harder to turn by hand — a quick no-meter check.
• The classic fault: a motor that vibrates or growls instead of turning almost always has its coils mixed up — a cable whose middle two wires are swapped relative to what the board expects, or one coil open-circuit (broken wire, pushed-out pin). It is rarely a dead motor.
• Direction: if a correctly-wired motor turns the wrong way, the fixes are inverting that axis in firmware or swapping one coil’s two wires — never re-pairing wires across coils.
• Connector order is not universal: Creality boards and third-party boards do not all expect the same pin order at the motor socket — which is why our Creality board pinout guide matters when a motor or board is swapped. Power off before plugging or unplugging steppers: pulling a motor cable under power can kill the driver.

Steps and current in the real world

With a 1.8° motor, the familiar stock Creality steps-per-mm values fall straight out of the mechanics (at 16× microstepping, before TMC interpolation):

Axis	Mechanism	Typical stock steps/mm
X / Y	GT2 belt, 20-tooth pulley	80
Z	T8 leadscrew, 8 mm lead	400
E (extruder)	MK8-style drive gear	~93 (always calibrate — see below)

The E value is the one that is never exactly right out of the box: gear bite, filament hardness and tension all shift it, which is why E-steps calibration exists and why it follows any extruder or motor change — the marking-and-measuring routine is in our Ender 3 calibration guide. As for driver current: set it for the job, not the datasheet maximum. Symptoms are the guide — too little and the motor skips steps under load (layer shifts on axes, under-extrusion or clicking on the extruder); too much and the motor runs painfully hot and can soften its mount. Warm in operation is normal; too hot to keep a finger on is not.

Quick troubleshooting

• Vibrates, doesn’t turn: coil pairs crossed or one coil disconnected — check the cable and pin order first.
• Turns the wrong way: invert in firmware or swap one coil pair’s wires.
• Skips under load: check mechanics (belt tension, binding, nozzle blockage on the extruder) before raising current — most “weak motor” reports are mechanical drag.
• Gets very hot: driver current too high for a 1.0 A motor, or the motor is stalling against a jam and cooking itself trying.
• Completely dead: swap its cable with a known-good axis at the board end (power off!). If the fault follows the cable, it’s the cable; if it stays with the motor’s driver channel, suspect the driver; the motor itself is the least likely culprit of the three.

Frequently asked questions

Is the Creality 42-40 a NEMA 17 motor?

Yes. “NEMA 17” specifies the 42 mm mounting face, and “42-40” adds the 40 mm body length. Any NEMA 17 motor physically bolts on — but match the step angle (1.8°), current class and torque, and check the coil pin order, before treating one as a drop-in replacement.

What is the difference between the 42-34, 42-40 and 42-48?

Body length, and with it torque. The 42-34 is the shorter axis motor of the Ender 3 generation; the 42-40 is the standard extruder motor (0.4 N·m holding torque, 1.0 A); the 42-48 is the longer, stronger version used on larger machines. Same face, same step angle — different strength.

What current should a 42-40 run at?

Below its 1.0 A-per-phase rating — the rating is a maximum, not a setting. The right value is the lowest current that doesn’t skip steps in that motor’s job, verified by temperature: warm is fine, too hot to touch means turn it down (or find the mechanical drag making it work so hard).

Why does my new stepper motor vibrate instead of turning?

Almost always the coil wiring order. Bipolar motors need each coil’s two wires on the correct pin pair; many replacement cables swap the middle two wires compared with Creality’s order. Check continuity to identify the pairs and match them to the board’s pinout.

Can I use a 42-40 as an axis motor, or an axis motor as an extruder motor?

A 42-40 on an axis is fine — it’s stronger than the usual 42-34. The reverse direction is the downgrade: a 42-34 on extruder duty has less torque headroom and may skip under extrusion load, showing up as under-extrusion that no amount of tuning quite fixes.