Bat shaving is a bat procedure that takes away the thickness of a bat’s inside barrel. The end cap is taken off and a digital precision lathe “shaves” the inner barrel. The taking away of composite materialallows the bat to flex more at the point of impact, which equals greater batted ball speed. Increased ball speeds can add 40-50 feet with shaving only, add bat rolling before shaving and that number goes up higher.
There are many people who open up a end cap and sand the inside with a drill hone (or drum sander). A sander will make “hot spots” and “dead spots” all through out the bat's barrel. A hot spot is when the spot is sanded too much and the barrel flexes more. This sounds great because we want more flex for more pop, right? Not exactly, this hot spot will actually be a weak spot on the barrel and increase the chance of cracking substantially. There are set measurements for bat shaving, which test the limits of the bat as far as strength and longevity. Shaving past these limits will make your bat to break early. The dead spots are just the opposite of hot spots; they make the bat to flex less, which causes a decrease in pop. A bat from the factory will often have inconsistencies of 5-10 thousands of an inch inside the barrel already. The precision lathing of a bat will actually sculpt the most precise wall on the market. A constant barrel wall allows the bat to have the same flex around the bat for increased batted ball speed and better durability. The main point is that sanding the inner barrel will never be precise, only a lathe can accomplish this. Most people who shave on EBay (and even some on the internet) utilize a drill hone (drum sander); this is why you will see low prices on EBay for shaving services. The lathe should have a digital read out to lessen the chance of inaccuracies. One run through the lathe is not as accurate as taking out material in 2-3 runs. It would be like sanding with coarse grit sand paper as opposed to a fine grit sand paper. The fine grit will take longer but it produces a superior product. When the bat is taken out of the lathe it will have lost 1-2 ounces of material depending on the manufacturer of the bat (different bats have different specifications). That weight needs to be put back into the bat at the handle and end cap, an extra amount can usually be put into the cap for an end load. If you did not know, all manufacturers create their barrels to weigh the same. They put metal weight into the handle and extra resin into the end cap to weight the bat anywhere from 26 ounces to 30 ounces. After the weight is added back the end cap is put back on using the correct glue, substandard glue could result in the end cap separating and even popping off.
Simple answer: Bat shaving removes layers of composite from the inside of a bat’s barrel in order to reduce the wall thickness. This is accomplished by using a digital CNC that takes material out. This reduction in the wall’s thickness allows the barrel to flex more. The increased flex also increases the batted ball’s mph which makes the ball travel much farther.
An altered bat can be called many things: Homerun derby bat, juiced bat, doctored bat, hot bat, glass bat, outlaw bat, or simply, a shaved bat. All these terms are the result of “shaving” a bat and normally exceed the certification stamp performance guarantee put on by manufacturers (in conjunction with softball, fast pitch, or baseball associations). Bat shaving takes composite material out of the inner part of the barrel. A thinner barrel will create a greater “trampoline-effect” when a ball strikes it. The bat will flex more at the point of impact which will cause a faster exit velocity and translate into quicker line drives and greater distances. The sweet spot of the bat will also increase up to 2 inches each way. Exit speeds increases are anywhere from 5.2 mph to 7.8 mph which corresponds to 30-60 feet in extra distance traveled.