The most diffcult process in the cavity BPM fabrication is the connection of the cavity part and the wave guide part. An idea to get rid of the process has been proposed, which is to fabricate the cavity and the wave guide as a single block by fabricating the wave guide using an end-mill. The inner corners of the wave guide have to be rounded if it was fabricated by an end-mill. We modified the existing design of the wave guide to coaxial cable adapter for Q-BPM employing rounded corners and for the signal frequency of the IP-BPM.