It’s pretty easy for bowlers to get slightly confused when it comes to axis rotation and axis tilt of a bowling ball. The axis tilt represents the spin that’s put on the ball while the axis rotation is the amount of side roll your turn applies to it. The tilt will increase when the circumference of the ball track is reduced. There’s less tilt with a high track and more tilt with a spinner.
When determining the tilt of the ball’s axis you’ll need to locate the axis of your ball's rotation. The best way to do this is to throw several balls along the lane’s oiliest part as this will leave you with an oil track all the way around the bowling ball. You can use a grease pencil to trace the oil track completely around the ball. The track for the initial rotation of the ball on the lane is closest to the ball’s finger holes and that’s the one you want to use. Most of the ball flare results when the track and axis changes when the ball is rolling down the lane.
When you’ve marked the initial track/rotation of the ball you can place it in side of a small ashtray on top of a table. Then rotate the bowling ball until the track becomes horizontal to the table. The next step is to measure the distance from the track which is on one side of the bowling ball over the top of the ball to the track which is on the other side of it. With the grease pencil you can mark a point on the top of the ball which represents half of the distance between the two sides of the track. You can then rotate the bowling ball a quarter of a turn while you keep the track horizontal and repeat this measuring process. The axis point of the ball’s rotation can be found if you mark the point where the two lines intersect.
The track of the ball determines the tilt of the axis. The ball’s circumference is 27 inches and if the track covers this it means there will be no tilt. This type of roll is usually a complete straight ball which rolls over the middle of the finger and thumb holes. A semi-roller track will cover less of the ball’s circumference and it will have some tilt while the spinner track has the most tilt. When the track covers the ball’s full circumference and has a tilt of zero degrees there are ways to determine the tilt of the other tracks.
The best way to measure the tilt of the axis is to mark the first track around the bowling ball by marking the axis point once you’ve found it. You can then place the ball in an ashtray on top of a table and rotate the bowling ball until the bottom of the track is in the middle of the bottom of the ball on the table. You then rotate the ball until the track faces you. This enables you to view the top and bottom of the track sitting in front of you.
Now you can mark a line right around the middle of the bowling ball. This line will allow you to measure the distance from the line to the axis and determine how far the axis is located from the center of the bowling ball. Fifteen degrees of tilt is represented by each 1 and 1/8 inches that the axis tracer is above the center line.