If the ball is thrown correctly, the ball will be able to curve left for a right-handed thrower and right for a left-handed thrower. The size of the curve depends on the practice that has been put in, however, with some practice a two foot curve is normally possible within a day of practice.
Brand new balls are not your friend; you need to take coarse sandpaper and use it against the whole surface of the ball to give it a rough feel. A ball that is smooth will not curve as well as one that has a roughed-one texture.
Place a chair or other flat surface where you will throw. When playing wiffle ball, a “strike-out zone” is marked beyond where the batter is. If the ball hits the area it counts as a strike. If you have a lawn chair then you will find that the back of it is a perfect choice. This means you have somewhere to aim for when you throw and also acts as a stationary object which helps you compare how the ball is curving.
First Step: Get The Grip Right
Regardless of whether you are right or left-handed, you need to hold the ball at the seams with your fingers (this is in the line in the middle of the ball which divides the solid hemisphere and the perforated hemisphere) you also need to have your eye along the seam which is opposite your middle finger. You need to get your index finger to stick up where your bum is. All holes need to be facing your bum and eye.
Second Step: Get The Throw Right
It’s hard to explain the specifics of the throw; you want to use a standard overhand throw and try different ways. You will find the touch should come naturally. As the ball releases let your wrist bend gently in a downward direction. The majority of the force should come through your middle finger. It simply takes practice. After a few minutes of practice you should see your first curve, but to get a larger curve will take a few more days of work.
- If you are throwing a curveball with a taped-up Wiffle ball you need to grip it the way you would a 4-seam fastball, but get your top two fingers to stay together. As you throw you want your elbow and wrist to snap over the top of the ball. This should make it sink and curve.
- If you are throwing a slider you should grip it like a 4-seam fastball but do the throw sidearm. The ball should spin like the earth. This should give a big curve and you may see the ball rise a little too.