Quantity   Component name
1 × [cutter] 0.1mm, 10deg V-bit A short bit to put inside the housing, the shorter, the better as it reduces the overall tool length. Example https://www.aliexpress.com/item/33058654975.html
1 × [shank] Old 3mm drill bit Old 3mm drill bit, cut to about 18mm length
1 × [spring] Aluminum beer can As a material for spring and lock
1 × [bit holder] See 3D model in files
1 × Hot glue gun To lock the bit in place