There are common traits that promote this:
(1) small hands with a bat that’s too heavy
(2) hands that loosen their grip, either because of the lack of concentration or weakness with the grip.
(3) the top hand takes the lead after the bat brakes the plane of the shoulders.
(4) the knuckles are so far off line to one another during the initial gripping of the bat, but during the swing they actually turn, therefore giving the hands a “wringing” motion on the handle.
(5) and finally, and the most common reason, the neck of the bat’s diameter is too small, thus the hands often overlap, and even a large space is viewed between the upper and lower hands with the grip…
All of these features will allow the bat to turn in the hands, thus causing friction.
If you’re using a wooden bat, a common after effect of making contact with the ball, is feeling the “BEE’S” in the hands. This term… the “BEE’S” is like a stinging sensation. When the bat is not held properly, and grain of the wood goes contrary to trademark during impact, the bat will actually vibrate so fast, all that vibration travels along the grain and right to the hands. Thus, a feeling of bee stings in the grip.