How to Use Washers and Spacers

Washers and spacers are rods of different thicknesses with a center hole, sized so a Shaft or Screw can easily pass through the hole.

The main purpose of the washers available with the VEX EDR system is to provide an interface between a stationary component and a rotating component to reduce friction. For example, when a washer is placed on a shaft between a shaft bearing and a shaft collar, it reduces the friction between the stationary bearing and the shaft collar fixed to the shaft by providing a free spinning component between them.

There are a number of purposes for spacers. One purpose is, spacers can be used to keep space between two components. This space could be needed so a component like a spinning wheel does not rub against an adjacent metal structure, or spacers can provide space between components on a shaft. For example, placing spacers between Intake Rollers on a shaft may provide a more efficient intake for competition game pieces.

Intake Roller

Another purpose for spacers is to keep a screw and nut from being over-tightened and deforming the component which is being mounted. Gears and sprockets with mounting holes have a molded center hub which protrudes out further than the gear or sprocket teeth. When mounting the gear or sprocket to a wheel or metal structural component, the screws should be inserted through the mounting holes of the gear/sprocket and then a spacer placed on the screws before the screws are inserted into the wheel or the metal structural component. These spacers need to be at least as wide as the gear, or sprocket’s hub protrudes. If this does not occur, when the screw is tightened with the securing nut, it is possible to over tighten the screw and deform the gear or sprocket.

Example of mounting a gear with spacers to a piece of structural metal

The available washers and spacers are:

Teflon Washers are the thinnest of the washers/spacers available and have a low coefficient of friction.

Steel Washers are very durable and are a good all-purpose washer.

Plastic Spacers are available in two thicknesses 4.6 mm and 8 mm. These black spacers are the smallest diameter of the spacers available and are ideal for applications where there does not need to be as much contact surface, such as on a shaft between a wheel and a piece of structural metal. These spacers also work well for filling in the space on a screw between a piece of structural metal and a gear/sprocket when they are being mounted together as mentioned above.

Nylon Spacers are available in ⅜” OD and 1⁄2” OD. Both varieties come in Variety Packs containing 4 different thicknesses. These spacers work well for applications where more support is needed from a larger contact surface, such as filling in the space on a shaft between a tower and an arm of a robot.

High Strength Spacers are designed specifically for the High Strength Shafts. The plastic High Strength Spacers come in a High Strength Spacer Kit which includes 4 different thicknesses of spacers. The High Strength Spacers have a center hole which is shaped to fit the High Strength Shaft and they will not free spin on the shaft.

Teflon Washer Steel Washer Plastic Washer Nylon Spacer High Strength Spacer

Note: The VEX Robotics Competition has a game rule about “Non-VEX screws” which allows any commercially available #4, #6, #8, M3, M3.5, or M4 screw up to 2” (50.8mm) long (nominal), and any commercially available nut, washer, and/or spacer (up to 2” / 50.8mm long) to fit these screws

There are locking washers commercially available such as the Split Lock Washers and the Tooth Lock Washers which can be used with Hex Nuts to keep the nuts from loosening. In addition, there are numerous other types and sizes of commercially available washers and spacers.

Wheels and other motion hardware can be purchased at https://www.vexrobotics.com/vexedr/products/motion.