My 15 year old Thoroughbred mare tries to bite the clippers, why? I have no clue. But then she always shakes her head to avoid it. Let me explain...
I can and always have been able to clip her legs and she is fine.
I can rub the clippers on/off around her entire body except her face which I can do when it is off. One day I was able to clip her entire muzzle, I would do one cut, then shut it off, praise, and repeat. Eventually that night I was able to cut her full muzzle without shutting it off. Now a few days ago I tried to do that and she would try and full out bite the clippers, the first time she did that I didn't know how to discipline her and my thinking time took so long so I couldn't discipline her. The next time she did it I slapped her in the nose, just like if she was trying to bite me.
She also has this little tactic, if she doesn't want you to clip her she will start shaking her head like there is a bug in her ear which there isn't because she never shakes her head until clipping time. I can be about a foot away from her with the clippers on and she will just start shaking her head like there is a bug in her ear. Then she will stop and if you move it closer she will just start shaking it again.
I have a very quiet clippers, we keep the blades sharp, and well oiled.