I recently purchased this router bit to try out but I am curious as to the purpose/function of the threaded bolt/nut on the top end of the tool shank. Is anyone familiar with this router bit? Thanks

Amana (PCD)Polycrystalline Diamond Router Bit
1/2" Compression Spiral DRB-200
https://www.toolstoday.com/v-8942-drb-200.html