Mini Bowling Ball Reaction/Layout Guide

by Jeff Piroozshad

Welcome, seeker of information.  On this web page, you will find the information that you've been looking for...if, that is, you've been looking for information pertaining to the proper way to map out a bowling ball to achieve the ball reaction you desire.

When drilling a bowling ball, there are generally three points on the ball that will influence the reaction of the ball after drilling.  They are the Locator Pin (Pin), the Center of Gravity (CG) and the Mass Bias (MB).  You will also need to know the location of your Positive Axis Point (PAP) and the general location of your track (the first flare) on the ball.  As a general rule of thumb (well, in my opinion anyway), the pin position controls what the ball does for the first 40 feet of the lane and the MB position controls what the ball does on the last 20 feet of the lane.  These two controlling factors combined with the surface preparation of the ball (dull, shiny, grit sandpaper or polish used) will control most of the ball's reaction.  This article will not cover surface preparation; still, it is important to understand that surface prep represents the majority of what a ball will do on the lane.

Center of Gravity                   Locator Pin Position                Mass Bias Position

Center of Gravity

We will start with the Center of Gravity, because it is the easiest to understand.  First off, the static weights resulting from CG placement only control about 5-10% of a ball's reaction.  This number used to be much greater, however, the dynamics of bowling ball cores and the friction generated by new ball coverstocks have given much more precedence to core positioning and surface than ever before.

The CG is usually marked on the ball with a punchmark, a small punched dot on the ball.  Underneath this punch mark, there are a couple of extra ounces of weight to make up for the roughly 2.5 ounces that are removed during drilling.  This way, the ball retains its balance and doesn't wobble down the lane because of the top of the ball being lighter than the bottom of the ball.  However, over the years bowlers realized that they could drill the holes on other places on the ball thereby shifting the CG to the side.  This changes the reaction characteristics because now one side of the ball is heavier than the other side, so the ball will want to lean more in that direction.

There are six (6) types of static weights that result from shifting the location of the CG away from the center of your grip:

  1. Positive Side Weight
  2. Negative Side Weight
  3. Finger Weight
  4. Thumb Weight
  5. Top Weight
  6. Bottom Weight

Positive/Negative Side Weight

Positive side weight means that the CG is shifted towards the side of the ball that is hooking into the pins.  If you're right-handed and throw a hook, it's the right side of the ball as you look at your grip with the fingerholes up and thumbhole down.  It is also the opposite side of your ball from where your track is.  This is the side of the ball where your PAP is located.  

Positive and negative side weights have effects on when and how much the ball will hook.  A ball with positive side weight will hook later and hook more.  A ball with negative side weight will hook sooner and hook less.

ABC/WIBC regulations place a limit of one ounce of side weight, either positive or negative.  This is measured by weighing the ball on a "dodo scale."  You compare the weight with the ball facing in one direction to the weight with the ball facing in the other direction.  The center of the grip faces up and for one measurement, the fingers are above the thumbhole and for the other measurement, the thumbhole is above the fingerholes (one day I'll get pictures of this and post them).

Finger/Thumb weight

Finger and thumb weight mean the CG is shifted up or down towards the finger or thumb holes.  Finger weight will make the ball go longer down the lane and have a snappier backend reaction.  Thumb weight makes the ball roll sooner and have more of a smoother arc when it starts to hook.

ABC/WIBC regulations place a limit of no more than one ounce of finger or thumb weight.  Again, this is measured on a dodo scale by comparing two sides of the ball.  The center of the grip again faces up, but this time, the finger holes face left on one measurement and right on the other measurement (you're comparing the finger half of the ball with the thumb half of the ball).

Top/Bottom Weight

As mentioned previously, bowling balls come with extra weight placed under the center of gravity punch on the ball to balance out the weight taken out by drilling holes.  This weight is called top weight because it is located in the top of the bowling ball.  Bowling balls generally are manufactured with anywhere from two to four ounces of top weight although it is possible to find balls that fall outside that range.  Lightweight balls are made with less top weight generally for two reasons.  Light balls generally are drilled for children so the holes are smaller, meaning there is less weight removed that needs to be balanced out.  Also, since the ball has less total weight, an ounce or two of top weight will have more effect on the ball's dynamics and throw them "out of whack."

Top weight has a similar effect as finger weight: the ball will go longer down the lane and snap a bit more on the backend.  Likewise, bottom weight is like thumb weight in that it makes the ball roll earlier and arc more.

Unlike other static weights, ABC/WIBC regulations allow up to 3 ounces of either top or bottom weight.  This is measured on the dodo scale by comparing the drilled side of the ball (top) to the non-drilled (bottom) side of the ball.

Top and bottom weight are not necessarily caused by shifting the CG away from the center of your grip.  They are more a result of how much extra weight the manufacturer placed in one side of the ball and how much weight is removed from that side during drilling.  However, you can alter top weight and bottom weight by shifting the CG.  Because top/bottom weight are measured by comparing the grip side of the ball (the top) to the non-grip side (the bottom), if you shift the CG away from the center of the grip, you are moving it around the circumference of the ball towards the bottom.  You would be removing top weight (and/or adding bottom weight depending on how you look at it) by shifting the CG.  Therefore, the most top weight you can have in any particular ball after drilling (and before drilling any extra holes) would be if the CG is directly in the center of the grip.


Locator Pin Position

When bowling balls are manufactured, the core of the ball is suspended in the mold by a plastic colored rod.  The coverstock is then poured around the core.  The plastic rod is then sliced off at the ball, leaving a bright colored dot on the balls surface about one-half inch in diameter.  This dot is referred to as the Locator Pin, or just the "pin," and represents the location of the center of the core.  By putting this pin in different positions when drilling a ball, you can achieve different ball reactions because the core will be aligned and will rotate in a different way.  As stated at the beginning of this document, the location of the pin controls what the ball does in roughly the first 40 feet of the lane.  It controls when the ball will change direction, how much the ball will flare and how much hook potential it will have when it does change direction.

There are generally four directions you can place the pin: high, low, towards the PAP and towards the track, or combinations thereof.  

High pin position

A "high" pin position means that the pin is located up towards the top of the ball.  The higher the pin is placed, the longer the ball will go down the lane before it changes direction.  One must be careful, for if the pin is placed too high, the ball will go too long and will change direction too late, if at all.

Low pin position

A pin located towards the midline (horizontal line midway between thumb and fingerholes - use to locate PAP), or even lower, will make the ball change direction earlier.  It is also important to note that if the pin is placed too low, the ball might flare or track over the middle finger.  There is something called "the safe zone" which is located above an imaginary line from the PAP to the middle finger.  If the pin is placed below this line, there is the danger of the flare hitting the middle finger.  If the pin is above this line, the ball is "safe" from this result.  Generally, this is only a problem for higher-track players and for high flare potential bowling balls.

Pin towards the PAP

The closer the pin is placed to the bowler's positive axis point, the earlier the ball will change direction.  Please note this does NOT necessarily mean the ball will hook more - only earlier.  There are ways to drill balls involving this method where balls will change direction earlier than most other equipment, but cover less total boards than most other equipment.

Also, a pin on the PAP will generally make the ball have zero flare potential.  This is because the core is in a very stable position.  Flare is caused by the core "realigning" itself in order to find a stable position to roll in.  A ball with the pin on the axis means that the core is laying exactly on its side and rolling much like a rolling pin that a chef would use to flatten out dough.  Again, this is a very stable position so the core has no work to do to find stability.

Pin towards the track

The closer the pin is placed to the bowler's track, the later the ball will change direction.  This is essentially the opposite of the previous description of the pin near the PAP regarding when the ball will hook.

However, this is very much like the pin towards the PAP regarding flare potential.  Pin on the track is also a very stable position.  The core is standing straight up and down relative to the axis on which it is rotating.  Because of this stability, the ball again will not flare much because it has no reason to find a more stable is already in a very stable position.

Pin between PAP and track

Although not an actual, physical "location," the vast majority of bowling balls are drilled where the pin is near the middle of these two.  If you put the pin at about 3 3/8" from the PAP, this results in a ball which has the core in a very unstable position.  The core is not laying on its side and it is not standing up either.  As a result, it will try to realign itself during its trip down the lane to find some stability.  This is what causes track flare, and the 3 3/8" pin position cause a LARGE amount of track flare because the pin will be about halfway between the track and the PAP.  The further from this 3 3/8" point you get, the less the ball will flare.  Going towards the axis will make it flare less and hook sooner...going towards the track will make it flare less and hook later.

Now you are starting to get the idea of how to "tweak" the pin position to accomplish the reaction you desire.  With combinations of vertical and horizontal pin location, you can make the ball do just about anything on the front 2/3 of the lane, which dictates how much hook potential it will end up having when it gets to the last 1/3 of the lane.

One note about pin position - Please notice how I prefer not to refer to pin placement relative to the bowler's ring finger, middle finger, etc.  The term "pin above the ring finger" and all others like it are totally meaningless.  Keep in mind that bowlers have different PAP's and different spans (distance between thumbhole and fingerholes).  A bowler with a pin above his ring finger can get a totally different reaction than someone else, and the pin can also be in a totally different place on the ball depending on the length of the bowler's span.  When referring to pin placement, please try to refer to it as a distance from the PAP and also how far above or below the midline.


Mass Bias Position

As I've said, I see the mass bias as controlling the reaction on the backend of the lane.  More specifically, it controls the SHAPE of the hook.  This is different than the amount of hook, which is nothing more than total boards covered.  Total boards of hook is more dictated by the flare potential the ball has combined with how much energy the ball has retained and how much energy the ball has already used.  Energy retention is affected by factors such as surface preparation, amount of oil, ball speed, revolutions, rev rate, axis of rotation and axis tilt. 

The mass bias of a bowling ball basically tells you in which direction the mass of the ball is biased towards (whoa, I'm sure THAT helped).  This is different than the center of gravity of the ball.  On balls that do not have symmetrical cores (Ebonite has a lot of these lately), or balls that are symmetrical in shape but not in density, where one side of the core is denser than the other (Storm likes to do this), it tells you where the heavier, denser, more massive (pick your favorite adjective) part of the core is.

What does this mean?  I have no idea.  However, I can tell you what happens when you put the mass bias marking in different places and how it will affect your ball reaction.  There are four basic locations you can put the mass bias on a bowling ball:

  1. On your track
  2. On your Vertical Axis Line (VAL)
  3. Halfway between the track and the VAL
  4. Past your VAL

On your track

This mass bias location, also referred to as a "1:30" drilling because the pin will end up at approximately a 1:30 clock position to the center of gravity (the CG being the center of the clock) will make the ball have an ARC reaction on the backend of the lane.  The reaction will not be very snappy and will generally be smooth.  

This also tends to be a good drill pattern for large, smooth, sweeping hook balls but only because the pin position usually ends up in a high flare potential position, not because of the location of the mass bias.  If you put the pin on your axis and the MB on your track, you will not get a very large hooking bowling ball because of the very low flare potential that comes with that pin position.

On your VAL

Ok, first...what the heck is the Vertical Axis Line?  It is very simple.  The Vertical Axis Line is a vertical line that goes through your Positive Axis Point.  For instance, my PAP is 5 3/4" right and 7/16" up.  The line you use to go "up" would be the vertical axis line...just extend the line about 6 or 7 inches in the down direction and you can use it for mass bias location.

When you put the MB on the VAL, the ball reaction shape will be forward roll.  When you want the ball to straighten out on the backend, this is the drill pattern that people go for.  It is also called a "10:30" drill pattern because the pin will end up being located at a 10:30 position from the CG.  I tend to use this drill pattern when I play outside the second arrow.  I figure from there, the ball has enough entry angle as it is, so I don't want any more "sharpness" on the backend than necessary.  This helps the ball straighten out and the entry angle is not too sharp.

Halfway between the track and the VAL

For all you brave souls (and those of you who want to see their balls do tricks), this is the "major flip" MB location.  When control on the backend isn't so important and you want to maximize your entry angle and power transferred to the pins, this is the way to go.  This also is a great MB location for playing the extreme inside angles like 5th arrow and deeper.  From that far inside, you'll need as much entry angle as you can generate to get the ball to turn the corner, hit the pocket, and still have enough energy left to kick the corner pins out.  When the lanes fry out, this is a great option if you would rather move deeper into the oil with an aggressive ball instead of staying outside with a mellower bowling ball.

As with all previous sections, you can also tweak the reaction by placing the mass bias between two of the locations described above to create a combination of the two.

Past your Vertical Axis Line

If you put the mass bias past your VAL, the ball will rev up a lot and very early.  Some manufacturers' drill instructions say that this is for "maximum revolutions" or "earlier hook" but it's all about the core being able to rev up harder and faster.  This layout is great for flooded heads and also for soft handed people who cannot get the ball to rev up enough to make a move to the pocket.  This also helps low-track players (spinners) as well.

One note about the mass bias - On asymmetric core bowling balls, the mass bias is marked on the ball.  Each company does this in different ways.  Storm uses an "MC2" while Ebonite uses a little picture of a bomb.  They are not difficult to find when they are marked.  However, balls with symmetric cores do not have a marked mass bias.  These balls still have a mass bias, but it will not be as strong with respect to reaction effect.  

To find the mass bias in non-marked balls, draw a line starting at the pin in the direction of the CG.  Draw the line through the CG.  Once you get to 6 3/4" from the pin, stop.  This is the mass bias point.  It is helpful to weigh the ball on a dodo scale before you do this because the CG is often marked inaccurately on bowling balls.

Another note about the mass bias - Similar to pin placement, one shouldn't refer to MB placement as a distance from the thumbhole because bowlers have different tracks, PAP's, etc.  This reasoning is the same as the note at the end of the pin placement section above.


(work in progress)


My thanks to: Bowling news, pros, and expert bowling tips.

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Copyright 2003, Jeff Piroozshad