Many metal clevis have a seam right down the side (take a look). Now if you hook that directly to the the highest vibration point on the aircraft then the seam can open and threads erode.

Metal to metal on a throttle arm (that metal pin in a loose metal hole) has historically been responsible for more mysterious losses than you can imagine. Years ago when our Rx's had far less signal to noise selectivity, This was a major problem and no metal to metal was SOP. Any two pieces of metal vibrating together at high freqency will without a doubt generate noise (RF noise) that will eventually interfere.

Our modern Rx's while much more selective are stiil vulnerble to this noise when conditions are right. I have seen losses due to this constantly. When new student shows up with this setup that airplane does not fly with me untill its eliminated . Never use a metal or metal pinned clevis on a metal throttle arm.

John