Gears, Sprockets, and Chain

Gears, Sprockets, Axles, and Axle Hardware


Axles provided by the Tetrix build system are D-shaft axles of various lengths and diameter. A D-shaft axle had a grinded flat edge on one side of the full length of the piece. This flat edge allows for additional elements to be mounted to it using set pins. A properly tightened set pin lined up with the flat edge of a D-shaft axle will create a very strong assembly. The tetrix axles come in two diameters, a 4.7mm and a 6mm. The 6mm matches the diameter of the motor shafts on the tetrix provided motors. The 4.7 mm axle comes in 100mm (3.94 inches) and 250mm (9.8 inches.) The 6mm motor shaft axle comes in one size of 100mm. 


Bushings, (sometimes called plain bearings, plain bushings, or sleeve bearings) reduce friction between two surfaces sliding against each other. Bushings work because of a principle that when two dissimilar metals are rubbing on each other, they have a lower coefficient of friction than like metals- this principle is bolstered when one of the metals is bronze. The Tetrix Bushing is bronze with an inside diameter of 4.75mm and an outside diameter of 8mm. This allows for the 4.7mm axle to fit snug and glide on the inside and have a good fit in the center 8mm hole of a structural tetrix element. The bushings come in two sizes, 11mm and 4mm, and also have a variant that fits motor shafts where the inside diameter is 6mm. 

Axle Collar

An Axle set collar is designed to lock a rotating axle and secure the horizontal alignment. When the set screw is tightened over the flat edge of a D-shaft axle the set collar will secure the side of the axle from moving past a structural element face. The tetrix set collars have an inside diameter of 4.75 mm which allows for a 4.7mm axle to fit perfectly with an outside diameter of 10.7 mm which is wider than the bushing face or 8mm hole on a structural element face. 

Axle Hub and Motor Hub

The Axle and Motor Hubs are used to attach gears, wheels, and structural elements to axles and motor shafts. They do this by mounting on the D-shaft axle and tightening their set pin on the flat edge just like the Axel Set Collar. Each hub has a protrusion that is 8mm in diameter that lines itself up concentric with a wheel, gear, sprocket, or center of a structural element. This is important to make sure any rotating elements are centered on the axle. The inside diameter matches to fit on a 4.7 mm axle or a 6mm motor shaft. The four holes on the face of the hub are tapped with a 6-32 screw thread that allows you to secure whatever you are mounting to the hub using a 6-32 Socket Head bolt without the need of an additional nut.


Tetrix Gears are made from Aluminum which provide them with enough strength to mesh with other gears without slipping or tearing. All tetrix gears have a center 8mm hole surround by four 9/64 through holes that allows for mounting to a Axle or Motor Hub. The gears come in three sizes:

With these combinations you can have a 1:3, 3:1, 1:2, 2:1, 1:1.5, or 1.5:1 gear ratio for added speed or torque.


Tetrix Sprockets are made from Aluminum which provide them with enough strength to mesh with chain tearing or snapping. Tetrix sprockets are designed to fit with #25 chain. All tetrix sprockets have a center 8mm hole surround by four 9/64 through holes that allows for mounting to a Axle or Motor Hub. The sprockets come in three sizes:

With these combinations you can have a 1:1.5, 1.5:1, 1:2, or 2:1 sprocket ratio for added speed or torque.

#25 Chain

#25 Chain gets its name by being .25 inches wide. The chain with links is made to work with all ratios of the tetrix sprockets. Chain can easily be cut to custom lengths using the chain breaker tool and connected to form a loop with a master link.

Master Link

A master link or quick-release link is a roller chain accessory that allows convenient connection and disconnection of a chain without the need for a chain tool. It acts as a set of the chain's outer plates, so joining two sets of the chain's inner plate ends. This allows you to break a chain to any length and then reconnect the two ends. A Tetrix Master Link is often reusable and will allow you to separate and reconnect the chain length as many times as you need. Caution: Do not lose any of the individual components of a master link or it will become useless.

Pinion Gear

The Tetrix pinion gear included in the Linear Slide pack is an aluminum 28 tooth gear that is 20.8mm (.82 inches) in outer diameter. The inner diameter is designed to fit snuggly on a 4.7mm axle. On the pinion gear is a nested set pin that is aligned and tighten on the flat edge of a D-shaft axle.

Rack Gear

The Tetrix Rack gear included in the Linear Slide pack is a plastic rack gear whose teeth align with the corresponding pinion gear. Each rack gear is 5 inches long and can be used alone or laid end to end indefinitely- as long as there is space. The plastic rack gear allows for any tearing or ripping of gears to happen on the rack saving the pinion gear making the racks consumable if not careful. The Rack has threaded holes for a 6-32 bolt at regular intervals that align to a tetrix channel hole pattern.

Rack Slide Blocks

The Rack Slide blocks that are included in the Linear Slide pack are made from plastic. This part does not typically see much wear and tear. The profile of the slide block allow the racks to slip through while also being supported as not to fall out or misalign. When mounting the slide blocks in between a channel element you must be sure to use the 5/16" Length Socket Head bolt when fastening into the side holes. If you use the bigger bolts, the bolt will screw into the rack preventing it from moving and damaging the rack.

Round Spacer

The Round Spacer is a lightweight aluminum spacer that is exactly half the width of Tetrix Channels and feature four tapped holes to provide secure 16 mm spacing between Tetrix structural elements. They can also come where the four holes are untapped through holes allowing a bolt to pass through. These handy spacers are useful for obtaining proper gear mesh spacing when building geared servo mechanisms and for a variety of other adjustments and attachment needs.

Round Spacer

The Round Spacer is ideal for maintaining proper distance between two Tetrix elements attached on either side of a structural part. The flat round spacer is 2 mm thick – the same wall thickness as Textrix structural elements- this makes it perfect to act as a washer to add space where needed to line up to other tetrix parts, wheels, gears, or sprockets. The inside diameter is 8mm (.31 inches) and the outside diameter is 27mm (1.06 inches) The patterns of the holes are identical to the other hole patterns on Tetrix's structural elements. 

Simple Assemblies

Rack and Pinion Linear Slide

Adding a forklift, conveyor, sorter, or other linear-motion component to robots is made simple with this assembly. A Rack and Pinion Assembly transfers the rotational motion of the pinion into linear motion of the rack. The rack gears can be used alone or laid end to end to create whatever length required and are attached to a Tetrix Channel. The slide blocks and pinion gear go onto another channel that slides across the rack gears when powered by gears and/or a DC motor or Servo.

Worm Gear Assembly

Worm Gears are used to transfer power at a 90° angle. Worm gears are ideal when you need power in a specific area but cannot fit or mount an actuator near the area. Using a worm gear, you can set you motor away and to the side and bring power perpendicular to the output shaft somewhere else.