Modern hanger thread is 10mm x 1mmpt. This is virtually the same (for the 6 or so threads engagement) as the older Campy thread of 10mm x 26tpi (and note the combo of metric and standard units, ask why and I'll tell you). It's quite possible that the hanger threads are distorted. The hole might not be round. The hanger could no longer be flat (thing potato chip like). The initial threads might be squished. I would consider chasing the threads only after confirming the hanger's shape condition. Any "blacksmithing" you need to do should go before the thread chasing. Andy