Rob Bailey’s Ball Fitting System

Introduction to Rob Bailey’s Ball Fitting System

A properly fit ball requires a combination of objective measurements blended with subjective conclusions.  This subjective part is the “Art of Ball Drilling”.  No one set of standards will work with all bowlers due to the infinite number of hands, strengths, and styles.

To make any span and grip system truly effective it must accomplish the following:

  1. Be easily reproduced and copied
  2. Use a grip centerline that lends itself to accurate and predictable ball layouts
  3. *Accommodate proper span and pitches that conform to the hand
  4. Make the ball easier to throw and make it feel lighter in the hand
  5. Allow the bowler to easily increase power and rev’s without sacrificing accuracy
  6. Do all of this and stay price-competitive in the marketplace

Tools required to do this best include a mill drill with digital gauges to accurately cut ovals, along with a pivoting jig and very accurate measuring tools to measure spans to the 1/64thof an inch. A pivoting jig allows you to move the ball to get exact on the cut line.  Taking a ball in and out of a clamped jig or vacu Jig does not allow that and is much less accurate and time consuming.

I would like to elaborate on point “3” above:


One must have a good understanding of how pitches work and the angle that thumbs and fingers go into the ball.  Let’s start with history; most balls drilled years ago in the early fingertip era had excessive reverse pitch and stretched spans, combined with forward, or at the least, zero pitch in the fingers.  Side pitches were relatively standard.  Some of this was helpful before finger grips became the norm, helping the ball to stay on the fingers longer.  Forward pitch is defined as the bottom of the hole going to the center of the grip, and reverse is away from center.

The system I employ looks closer at the hand (like all good systems) and accommodates inflexibility that may be present in fingers, creating back-pitch (reverse) in most fingers, along with hand condition (dry or moist).  With grips, back-pitch (reverse) in the fingers is not a deterrent, as fingers easily stay in the ball.  Side pitches are also a consideration, based on the degree of angle present when a hand lies on a properly fit ball.  An average angle the fingers form from the centerline of the grip in a properly fit ball is approximately 15 degrees.

Also, most bowlers can benefit from far less reverse pitch in the thumb, and even forward pitch.  The most important factor in thumb pitch is directly related to the degree of angle a thumb goes into the ball.  Most thumbs are at a 40-45 degree angle (measured from a 90 degree line from the centerline of the grip) most ball drillers do not understand that 0.250 reverse pitch and 0.250 right pitch (for a right hander) add up to a “0” pitch effectively.  I call this pitch measurement the “Effective Thumb Pitch”.  Likewise, pitches of 0.250 left and 0.250 forward also add up to “0” effective pitch (for a right hander).  I have one customer that requires 0.560 right pitch in his thumb to properly exit.  He also has 0.360 reverse (almost 3/8ths).  However, based on the angle his thumb goes into the ball, it adds up to 0.100 effective forward pitch!

Earlier in my career, I was a bowler that was fit with the typical ¼ (0.250) reverse, however, my thumb required 0 side pitch and maybe even 1/16 left.  I always had to squeeze to hang on to the ball.  Every ball fitter came up with a different span, usually too long.  I had a friend with close to the same span and thumb size, but he had ¼ reverse and ¼ right and his was easy to hang on to but the right side pitch bothered my thumb.  His effective thumb pitch was 0 and mine was about 5/32 reverse, with both balls having 0.250 reverse pitch on the centerline of the grip.

“Over the Top” Problems:

Most ball fitters do not get the hand laid properly on the ball and have the hand lifted up on the side of the little finger.  This causes an over-span of the big finger, and an under-span measurement of the ring finger.  Most of these balls end up drilled with a “dropped” ring finger.  This, along with a stretched span on the big finger causes the hand to come over the top on release and does not distribute weight or lift evenly on the hand between the two fingers.

Too much reverse pitch in the thumb also causes an “over the top” release because the bowler is squeezing the ball to hang on to it, and would drop it if he or she did not turn their hand early.

Forward pitch in fingers, unless the span is quite short (which feels uncomfortable for most bowlers) causes excessive pull on the thumb, falsely creating a situation that requires effective reverse pitch to come out of the ball without “hanging up”.  This is still how I see most balls drilled that new customers bring in.

Turning finger grips to accommodate the angle that fingers go into the finger holes may or may not be an answer for most bowlers.  For years I turned my grips 15 degrees to the right based on the 15 degree angle mentioned previously.  This is more important with lift grips than ovals.  Turning grips can lead to a tendency to pull “over the top” on your release, so this is an individual preference.   I have no problem experimenting with this depending on the bowler.


Left  v.s. Right thumb pitch (or vice versa for a left hander)  Bill Taylor drilling guide

Again, because there is an effective pitch for thumbs, it’s the effective add up of the forward/reverse and the right/left that counts.  For example.  many times a little less right or left is required based on forward or reverse.  My experience is that with a thumb coming out of a hole at a typical 45 degree angle, the Bill Taylor ball drilling guide is still pretty accurate.  I cannot help but think Bill Taylor knew the principles I am talking about, but never mentioned the effective pitch.  His span measurement system is still fairly accurate to this day.  Even his pitch recommendations are fairly good.  It’s just that ball drillers did not follow the guide, putting in far too much reverse based on span, and stretched spans too far.  I’ll explain how this happens later.  Also, for today’s power game and the use of grips, finger pitches need to be different from his recommendations.  His book on drilling is still a “go to” and should be required reading for every ball driller, in my opinion.

Too much lateral pitch either way will still cause a problem on the opposite side of your thumb, and too much right, a problem on the left side of your thumb.  A hand that requires a lot of right pitch cannot be forced into a left pitched thumb hole and vice versa!  Again, it’s the effective pitch that counts.  A tendency to put left pitch in a hole strictly to accommodate forward pitch is not good ball fitting.


Finger pitch relationship:

Hands that require more right pitch generally need more right in fingers, and 0 or more left in the thumb leads to a benefit of more left in the fingers.  Reverse in fingers is more possible because of grips, especially the VISE VACU-GRIP system, as bowlers do not need forward pitch to “hang on” to the ball.  The amount of reverse is directly related to finger stiffness in the last joint.  An exception might be in kids; even though the hand might be quite flexible, I rarely drill a ball without at least 0.200 reverse in fingers so as not to cause a pull on the young and developing hand.  Typical finger reverse pitches I see range from 0.200 to 0.600 reverse, with outliers up to over 1 inch (1.000) and down to 0.  I have not drilled a ball with forward pitch for so long I cannot remember.

The advent of bowlers not using their thumb also changes everything.  Finger pitches for bowlers using their thumb vs not using their thumb are not that much different because a bowler not using his thumb has the ball lying on the hand as good as it gets!  Why not incorporate this into how you pitch fingers for bowlers that use their thumb!  Usually finger pitches need to be more left for right handers, and more to the right for left handers.  


Problems I See and Corrections Made:

I see most bowlers with fit problems coming in to the shop with forward in the fingers, too much reverse in the thumb, over-spanned on both fingers, especially the big finger, and a large contingent with a dropped ring finger.  Most bowlers with an arsenal of balls do not have any 2 balls that match, much less all of them.  Occasionally I see some good spans but I haven’t seen one yet that we could not improve, this based on results from the customers.   Bowlers come out of our shop with the best fit they’ve ever had and cannot believe how much better their hand feels.  This being said, we do make compromises on spans and grips based on bowlers body types, and the way they feel comfortable rolling the ball, so no one exact system or method will apply to every bowler.  That’s where the art of drilling comes in.  The real magic in drilling is the art, and also keeping accurate records, checking hands as they age or as a bowler changes his or her style, and being able to repeat drillings.  We cannot please everyone all of the time, but we can please 99% of the bowlers 99% of the time which is pretty good odd’s!

It should be noted that my system of drilling incorporates ideas from many sources.  I had mentioned Bill Taylor’s drilling guide for one, and IBPSIA has developed many good drilling techniques, along with Mo Pinel and others.  I started drilling balls in 1976, and over that course of time I have learned much from others, and much from application their drilling methods and mine.  I am sure we will learn even more.  There is always new idea’s to explore.   One must be wise enough to sort out all of the information out there without falling into the trap of buying into methods that simply make drilling more complicated than it needs to be.

A bowler can create his or her own span problems by releasing the ball incorrectly or inconsistently.  Invariably we get calls for lessons.  I will not do a lesson unless a ball fits properly, because ball fit is usually the weakest link in the chain, the shortest stave in the barrel, or, in other words, a bad grip will make it impossible to get a correct and repeatable release.  Also, someone constantly changing a release could have problems with any ball fit.  A good fit should allow a variety of releases, but it cannot make up for gripping a ball wrong.  The use of tape is extremely important as urethane thumb slugs will get very smooth.  I like the textured tape in the front at your thumb angle, and black fitting tape or electrical tape in the back of the hole, straight across.


  1. A well drilled grip will endure over time.  A grip that does not accommodate correct spans or pitches will wear down the bowler and the hand.
  2. All grips and pitches need to be made relative to a grip centerline so one can accurately record and keep track of measurements.  Once a measurement is made, no matter what method you go about getting it, it needs to be recorded in this fashion.  For example, if a grip is laid out and a thumb (or fingers) are then shifted one way or the other, you are basically changing the span and pitches relative to the center line, and more importantly, you change the effective thumb and finger pitches based on the degree the thumb and fingers go into the ball.  So, if for some reason you think this works, re-measure what you came up with on the grip line, and determine new hole pitches based on the grip line.  This will make the span easy to repeat.  Any other method of measuring becomes highly subjective and can leads to errors in repeating a drilling.
  3. The definition of a correct bowling grip will be somewhat different for each bowler, and there is a range of correctness.  One article I read referred to a “safe zone” for spans.  I agree with this.  It is not an exact science.
  4. The skill required to measure a hand and convert that to a drilling will vary by ball drillers and that’s where it really becomes an art and a skill.  Just like playing a musical instrument, singing, painting, drawing or anything else that is an art, some of us will be better than others no matter how much we practice.  Sports require many skills, including hand/eye coordination that some of us will have and some will not, no matter how much we work on it.  Ball fitters require the artistic part of the equation, and ball drillers require the skill of using the tools available.  In any case, practice and experience helps.  Some people are naturals at this and some are not.  Over the years I have trained many.  Some are very good and some are average at best.  The ones working in our shop are very good.

In this initial article, I am not touching on the details of fitting and drilling, much less the relationship of this to ball layouts.  This will need another chapter!



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