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How To Layout a Bowling Ball: Dual Angle Layout Technique

How to layout a bowling ball for drilling is one of those things that seem mystical. Some ball drillers make it seem like magic, or that they are performing huge mathematical computations before drilling a bowling ball.  Here is a simple technique that anyone can use to layout their bowling ball.

One caveat to this technique is that you must know your Positive Axis Point. You need to be consistent in your approach to help you find it. That is a whole article in itself.

Now, for the Dual Angle Layout Technique.

There are 3 pieces of the equation for this technique to work.

Drilling Angle

The first angle is a different measurement for the two types of balls, which are balls with both symmetrical and asymmetrical cores. The first angle is referred to as the "drilling" angle.

The drilling angle for a ball with a symmetrical core measures the angle between a line drawn from the pin through the center of gravity (cg) and the line drawn from the pin through the PAP.

For ball with an asymmetrical core, the drilling angle measures the angle between the line drawn from the pin to the preferred spin axis (PSA) of the ball and the line drawn from the pin through the PAP. The PSA of an asymmetrical cored ball also denotes the high RG axis of the ball and is referred to as the “mass bias” mark on the ball. The vast majority of manufacturers mark the PSA with a locator pin or a symbol. But, be careful because one manufacturer has chosen to mark the intermediate RG axis on one of their balls with a symbol and a locator pin instead of the PSA. Do your research. The pin on both types of balls is the low RG axis of the ball.

The reason the drilling angle is different for both types of balls is that a ball with a symmetrical core does not have a PSA before drilling. A ball with an asymmetrical core DOES have a PSA before drilling which allows the driller to draw the line from the pin to the PSA.

The drilling angle is the first decision the ball driller will make when using the DUAL ANGLE LAYOUT TECHNIQUE. The range of drilling angles to choose from is from a minimum of 10° and to a maximum of 90°.  A 10° drilling will roll the soonest of all the effective drilling angles.  A 90° drilling angle will roll the latest of all the effective drilling angles.  Always keep in mind ; the entire spectrum of effective drilling angles is from 10° to 90°.  Drilling angles of 30°, 50° and 70° provide drillings that roll up between the earliest rolling 10° drilling and the latest rolling 90° drilling.  Using a small drilling angle (minimum of 10º) will cause the ball to roll sooner. Conversely, using a large drilling angle (maximum of 90º) will cause the ball to roll later. A ball driller may choose any angle between 10° and 90°. The common drilling angles used are 10°, 30°, 50°, 70° and 90°.



Pin and PSA distances to PAP for different Drilling Angles



Pin to PAP Distance

The pin to PAP distance is the second component of the DUAL ANGLE LAYOUT TECHNIQUE. The flare potential of an undrilled ball is dominated by the total differential RG of the designed ball. The coverstock can have a small effect on the flare potential of the ball. The pin to PAP distance is used to control the amount of flare of the drilled ball and determines what percentage of the ball’s flare potential the drilled ball will have. This measurement has been a key component of all drilling techniques used since flaring bowling balls have been designed and manufactured. Larger flare patterns increase the friction between the bowling ball and the lane surface because there is a greater amount of fresh surface (no oil contamination) between the ball and the lane on larger flaring balls. The amount of flare resulting from the pin to PAP distance chosen is different for balls with symmetrical and asymmetrical cores. A ball driller should choose the pin to PAP distance for the ball being drilled to achieve the desired amount of flare. The amount of flare of the drilled ball will depend on the total differential of the undrilled ball and the pin to PAP distance chosen. The following charts show the different flare characteristics of both symmetrical and asymmetrical cored balls.




The Angle to the VAL

The angle between the pin to PAP line and the VAL is the third, and final, component of the DUAL ANGLE LAYOUT TECHNIQUE. This angle is as important as either of the first two components of the DUAL ANGLE LAYOUT TECHNIQUE. The data provided by three dimensional CAD modeling of drilled bowling balls emphasizes the extent to which the RG, the intermediate (asymmetrical) differential, and the total differential of the drilled ball can be changed from those specifications of the undrilled ball. The CAD study was done by Steve Freshour of Parkersburg, WV with a Solid Works program. Changing the angle between the pin to PAP line and the VAL has a very significant effect on how much the RG and the total differential of the drilled ball changes from the same specifications of the undrilled ball. The angle between the pin to PAP line and the VAL is effective from a minimum of 20º to a maximum of approximately 70º. Using the minimum 20º angle between the pin to PAP line and the VAL will result in the drilled ball revving up quickly and transitioning the fastest at the breakpoint. Using the maximum 70º angle between the pin to PAP line and the VAL will result in the drilled ball revving up slowest and transitioning theslowest at the breakpoint. Using a smaller angle between the pin to PAP line and the VAL (minimum of 20º) will lower the RG and increase the total differential of the drilled ball. These changes will result in the ball revving up faster and transitioning quicker. Conversely, using a larger angle between the pin to PAP line and the VAL (maximum of approximately 70º) will raise the RG and lower the total differential of the drilled ball. These changes will result in the ball revving up and transitioning slower. A ball driller should choose the angle between the pin to PAP line and the VAL to achieve the desired breakpoint for the bowler. The following charts show the change in the mass properties (RG, asymmetrical differential, total differential) between the undrilled ball and the ball drilled with the pin to PAP line at three different angles to the VAL.



I am going on record as saying that the limit is not 70º. If you are not familiar with the popular Rico Layout, it has a second angle of 90º.

The Method for a DUAL ANGLE Layout


  1. Draw a line from the pin through the CG (for Symmetrical Bowling Balls) or the Mass Bias (for Asymmetrical Bowling Balls)

  2. Draw a second line at an angle between 10° and 90°

  3. Mark your desired PAP from the Pin distance along this new line

  4. Flip the bowling ball around and draw a third line at an angle between 20° and 90°, this is your Vertical Axis Line (VAL)

  5. Now from the PAP (#3 above), draw a line perpendicular (90°) to the line you drew in #4, this is your midline

  6. Now use your PAP measurements to determine the middle of your grip



The beauty of the Dual Angle Layout Technique is that it allows the ball driller to keep the desired ball reaction in perspective when matching the bowler to the lane condition. By making a good decision in choosing the Pin to PAP distance, the ball driller can determine the amount of friction between the ball and the lane by controlling the track flare of the drilled ball. Once the amount of friction is determined, the ball driller can shape the breakpoint by choosing the drilling angle and the angle to the VAL. Adding the drilling angle and the angle to the VAL together will allow the ball driller to choose how quickly the ball will transition from skid to hook to roll.

If the two angles add up to 30°, the ball will transition as quickly as possible. If the two angles add up to 160°, the ball will transition as slow as possible. Keep the sum of the two angles between 30° and 160° to create effective ball reactions while still allowing the ball to maintain hitting power. Yet the drilling angle must still be kept between 10°and 90° and the angle to the VAL between 20° and approximately 70° (depending on the bowler's track).

Smaller angle sums should always be used for:

  • Speed dominant players

  • Higher axis tilt players

  • Longer oil patterns

  • Higher volumes of oil on the lane


Larger angle sums should always be used for:

  • Rev dominant players

  • Lower axis tilt players

  • Shorter oil patterns

  • Lower volumes of oil on the lane


Medium angle sums should always be used for players whose ball speed and rev rate match.

Keep this in mind -- the sum of the drilling angle and the angle to the VAL determines how quickly the ball transitions from skid to hook to roll. Using a smaller sum of the two angles will turn translational energy into rotational energy faster. And the shape of the breakpoint can be controlled by changing the relationship between the drilling angle and the angle to the VAL.

  • Larger drilling angles in relation to the angle to the VAL will create later, sharper breakpoints (more backend).

  • Smaller drilling angles in relation to the angle to the VAL will create a sooner, heavier roll (more midlane).



Using the DUAL ANGLE LAYOUT TECHNIQUE™ developed by MoRich, allows the ball driller to design precise ball reactions by choosing the drilling angle, the pin to PAP distance and the angle between the Pin to PAP line and the VAL. By knowing the dynamic potential of the undrilled ball and the ball reaction desired for the bowler, the ball driller can create the exact ball motion for every bowler by using the Dual Angle Layout Technique. Once the ball is drilled, it is easy to make surface adjustments to adjust the ball reaction for different lane conditions, oil patterns, and lane surfaces.

Bear in mind, the degree to which DUAL ANGLE layouts will be successful depends on the ability of the ball driller to make good decisions for all three components of the system.