i found the hole but discovered the spring was broken off in it. I drilled the broken piece of spring out of the hole, but the spring was too short to apply enough tension to operate the safety cam correctly. So I screwed a small socket head screw into the hole to act as an extension. I put the spring into the socket in the screw head and now I have an adjustable tension spring and the safety cam works correctly. As the old saying goes, necessity is the mother of invention.