Time to read: 4 min

A 3D printing toolbox isn’t complete without the spare components necessary to build, maintain, and fix a machine. Below we highlight what each of those compnents are and what they are used for.

Nuts & Bolts & Washers

3D printers commonly utilize metric components, ranging from M2 to M10-12 components for desktop models. The “M” in metric components refers to a number of millimeters associated with the crucial part of the hardware. For nuts and bolts/screws, the number is expressed as the width of the threaded portion of the hardware. Example: the post of an M5 screw and the hole of an M5 hex nut are both 5 millimeters in width. Depending on complexity and size, a 3D printer can use hundreds to thousands of screws, bolts, and nuts in its construction. Having spare M3, M4, and M5 fasteners ensures that fixing or modifying a 3D printer is as simple as reaching into a toolbox instead of making a trip to the store.

Matching hex wrenches and socket wrenches are crucial for manipulating nuts and bolts/screws in 3D printers, even for fully-functional units sold with no associated hardware or tools. Washers help distribute the force from a screw or bolt across the face of the object into which they are inserted. Without a washer, screws can easily exert too much pressure over too small an area of a 3D printed part – especially in RepRap 3D printers. They can also help space components along a bolt or screw, enabling fine adjustment of various components. Shims are extremely thin washers that help with spacing, enabling the user to make very fine adjustments. They should not be confused with washers or used to distribute loads from screws or bolts being used for structural strength.


Useful for adjusting and maintaining tension, especially in extruder idlers and at the ends of axes, springs are simple yet important components in some 3D printers. It should be noted, however, that not all 3D printers require springs to operate or include them in the operation of their extruders.

Bushings & Bearings

Bushings and bearings are used to help components move along rods. They allow parts to spin or move smoothly in a linear fashion; but can also be used for a wide range of other applications including acting as belt idlers or extruder block idlers. In 3D printers, sleeve bushings use a smooth material on their inner surface to allow motion along a rod, while allowing their exterior housing to rest inside a piece of hardware that keeps it captive. Bearings (or rolling-element bearings) consist of an inner ring and outer ring separated by ball bearings while containing them internally. This enables very smooth travel along rods or free-spinning motion over bolts and screws. Their essential purpose is to reduce rotational friction and support radial as well as axial loads.

Threaded Rods & Smooth Rods

Rods, either smooth or containing screw threads, enable a printer to have components with linear motion. RepRap 3D Printers sometimes use threaded rods as framing elements, while smooth rods are used in all varieties of printers as foundational elements in their axes – especially those which must hold hardware with bearings.


A coupling joins two elements of a machine together, enabling disparate elements to share an axis of motion or a motor.

Linear Rail & Car

Much like smooth rods and bearings, a linear rail and car enable motion in a single axis. Due to their larger footprint, linear rails are much more stable than rods when forming the axes of a 3D printer. They are also somewhat more expensive. Linear rails and their accompanying cars (or carriages) are equipped with very slick surfaces, allowing the car to run along the rail with virtually no friction. Combined with a belt and motor, very finely-tuned motion can be achieved.


In 3D printing, stepper motors enable components to move with a high level of accuracy and to adjust their movement on the fly. Thus, a printer can very quickly cause its printhead to move in complex shapes over the printing surface – creating complex 3D printed geometries. At their core, stepper motors divide the full rotation of their internal shaft into a number of steps. The motor’s position can be commanded to move and hold at one or any of the steps at any time. Stepper motors are more costly than conventional servo motors, but much more precise. In 3D printers they produce a slightly musical sound, especially when driving the printhead in curves.

Timing Belts

Attached to a pulley and affixed to a motor, timing belts enable a 3D printer to push and pull its axes with a high level of precision. The number of teeth in timing belts is tightly controlled, along with the shape of the teeth and distance between teeth (also known as pitch). They are designed not to slip and must be kept relatively tight in 3D printers to avoid missing steps while printing and causing errors in printed objects.