• Billiards Instruction: CueTips #68 – Knowing Where the Cue Ball is Heading

    What we are going to do this week is add to your arsenal of tools to move the cue ball accurately around the table. We are going to learn two “rules” for predicting the path of the cue ball after contact with an object ball. Knowing the path the cue ball will take off the object ball gives us the knowledge to direct the cue ball where we want it to go.

    The first skill we need to have is to be able to shoot a stop shot at various distances. A stop shot is one where the cue ball hits the object ball full and is sliding at the moment of contact. How we get the cue ball to be sliding is part of the art of pool. We can hit the cue ball higher and harder or lower and slower, but with the right speed, the cue ball will be sliding at the moment of contact and stop.

    Before we move on to the “90 degree” rule, let’s practice some stop shots. Here is a great progressive drill that will help you learn how to hit a stop shot from various distances.


    The object of this drill is to hit a stop shot and have the cue ball stop in the shaded area. You can’t hit the end rail! When you do it from one diamond, move the cue ball back a half diamond. Keep moving the cue ball back a half a diamond after you make the stop shot. When you fail to make the stop shot and/or stop the cue ball in the shaded area, move the cue ball up a half diamond. What this drill will do is give you is the feel necessary to hit a stop shot at various distances. Keep track of your progress. How far back can you get with 15 shots?

    Once you can make the cue ball stop at various distances, you are ready to learn the 90 degree rule. Before we get in to the details of the 90 degree rule, there is some vocabulary I want you to understand. First is the tangent line. This is the line at right angles to the cue ball path measure from the edge of the object ball. The stun line is the line at right angles to the cue ball path measured from the center of the ghost ball position at contact. Many people use the tangent line but mean the stun line!

    Ok, here is the 90 degree rule. If the cue ball hits an object ball at an angle, and is sliding at the moment of contact, the cue ball will move off at a right angle to the original path. That’s a lot of words and it is easy to see in a diagram.


    What I want you to see here is that if cue ball ‘A’ is sliding at the moment of impact with the two ball, the cue ball will follow the red path stun line. Notice how the stun line is half a ball width inside the tangent line. The beauty of knowing this is that once you are able to hit a stun shot, you will be able to accurately predict the path the cue ball will take after contact with the object ball.

    Here is a great old-time drill to help you get a feel for using the stun line.


    The object of this drill is to pocket the nine ball with a stun shot, and have the cue ball just reach the one ball. Once you can do that, just reach the 2 ball etc. This will fine tune your ability to control the direction of the cue ball with speed and a sliding ball.

    There is more to learn about the stun shot, but for now this is the key point. Realize that on all angle shots, the cue ball, even when sliding, picks up about a half a tip of running english. Keep that in mind when you plan a route having the cue ball hit a rail. The other point to keep in mind is that if you need to go a little ahead or behind the stun line, you can adjust your stroke accordingly.

    Now you know what all the great players are looking at when they sight down the stun line. They want to know exactly where their cue ball is going.

    Now on to the 30 degree rule. What the 30 degree rule says is that when the cue ball hits an object ball at an angle and is rolling, The cue ball will leave the object ball at about a 30 degree angle. You can see what a 30 degree angle is by making a peace sign. The angle between your two fingers is about 30 degrees. Please realize this is an approximation and the angle will change with different hits, but as a general rule, a rolling ball comes off the object ball at a 30 degree angle. Here is what this looks like on the table.


    The angle the cue ball takes off the six ball if it rolling is about 30 degrees. To measure this, use the center point of the ghost ball at contact as the center point for your 30 degrees. I use the the space between my knuckles as the starting point and estimate the 30 degrees.

    One point here to keep in mind is that this requires a pure rolling ball. One way to get a rolling ball is to hit the cue ball one tip above center. Another way, particularly on longer shots, is to stroke the cue ball in the center, and with the correct speed, the cue ball will be rolling when it hits the object ball.

    The best way to practice this is to set up a cut shot and then put a piece of chalk on the rail where you think the cue ball will hit the rail. Then shoot the shot. How did you do? Keep at this for a week and at the end of the week, you will know exactly where the cue ball will hit the rail.

    Good luck with this knowledge. Put the time at the table to really understand these concepts and you will be moving the cue ball like a professional player!



    Mark Finkelstein is the House Pro at Slate Billiards on 21st Street in Manhattan.If you have questions, or would like to see a particular topic addressed, you can email Mark at mfinkelstein3@verizon.net.
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