A grinding wheel assembly to be mounted on a vertical drive shaft extending from an electric motor through a horizontal table of a grinding apparatus. The grinding wheel assembly includes a core element that is rigidly secured to the drive shaft. A drop-on cylindrical grinding bit of the grinding bit assembly is slidably engaged onto a cylindrical portion of the core element. A slot is formed in the cylindrical portion of the core element and a ridge is formed on the internal bore of the grinding bit so that when the grinding bit is placed on the core element, the grinding bit will rotate upon rotation of the drive shaft.