For RC hobbyist, reamers are must have tools in their tool boxes. There are 2 major types of reamers, one of them is for reaming holes on bodyshells, the tip of the reamer is in cone-shape, user can control the diameter of the hole. The other type of reamer is for reaming the hole of the plastic parts, for getting a smoother surface inside the hole to achieve smoother movements of the parts, usually apply on composite suspension parts like the under A arms, C-hubs and uprights. The tip of this kind of reamer is in tube shape, users need to purchase different size reamer for reaming different sizes holes.
Tappers are used for cutting screw threads in a hole, usually metal parts from RC cars are pre-threaded, but most of the plastic or composite parts are not threaded and sometimes hobbyist, especially young ones may find it very hard to install the screws into those part, the better quality of the materials, the harder to build. So a proper tapper can help a lot. We have some commonly used tappers for RC cars, just make sure which type of screws you are using than find the right one to help you to build your machine.