Toy Spare Parts, Screws, Gears and Connectors

Measure thread, bore and tooth count before ordering

Small parts only work when the dimensions match, so read the numbers. A screw such as M4 by 20 millimeters has a four-millimeter metric thread and a twenty-millimeter length; measure the thread diameter and length of the original, and note the head shape. Nylon thumb screws can be tightened by hand but are not as strong as metal, so they suit light assemblies. Wheels are listed by diameter and width, plus the bore that fits the axle.

Gears have more variables. Tooth count sets the ratio, the module or pitch must match the partner gear so teeth mesh, and the bore must fit the motor shaft or axle, often a few millimeters across. A plastic spur gear in a multi-pack suits light loads; heavier loads need metal gears. Buy a pack with a spare or two, since small plastic parts are easy to lose or strip.

Joysticks, propellers and connectors that need a partner part

Some parts only make sense with a matching board or model. Arcade joysticks are described as four-way or eight-way, and many can be set to either: four-way registers up, down, left and right only, eight-way adds diagonals. Many use a five-pin connector or microswitches wired to a control board, so check the pin layout before you connect it to a controller or arcade kit.

Propeller accessories and FPV cameras belong to flying models. Propellers are sold by diameter and pitch and come in clockwise and counter-clockwise versions, so a quadcopter needs the right pairs. FPV cameras are chosen by video format, voltage and size. Wheels and axles for small robots are matched by axle diameter, so measure the axle before you order a pair.

Questions about Toy Spare Parts, Screws, Gears and Connectors

How do I measure a screw?

Measure the thread diameter and the length. M4 means a four-millimeter metric thread. Length is measured from under the head to the tip, except for flat countersunk heads, where the whole screw is measured. Match the thread pitch too if the hole is threaded.

What is the difference between four-way and eight-way joysticks?

A four-way stick registers only up, down, left and right, which suits maze and puzzle games. An eight-way stick also registers diagonals, which fighting and platform games use. Some sticks can switch between the two, so check the description.

Will a spur gear fit my motor shaft?

Check the bore diameter against the shaft diameter, and the module or pitch against the gear it meshes with. A bore slightly too small or large leaves the gear loose or unusable. Tooth count then sets the speed ratio between the two gears.