What Are the Effects of an Offset Thumb Hole in Ball Drilling?

What effect does moving the position of the thumb hole have when your ball is getting drilled?

A number of bowlers recommend an offset thumb, where the thumb hole is drilled slightly to the side of center. There are diverse reasons why a bowler might be curious about trying it. For example, one bowler who recently wrote to BeginnerBowlingTips.com, for example, has a thumb that isn’t as flexible and straight as the result of a past injury.

So is offsetting the thumb a good way to go?

It turns out there’s an interesting debate on the point.

In fact, one school of thought among experienced bowlers is that there’s actually no such thing as an offset thumb!

To be fair, they’re actually arguing that the word “offset” in a literal sense is a misnomer and not accurate, even if the hole itself is. And based on the geometric angles formed in the triangle of your thumb, middle and ring fingers, this makes sense. The center of your grip changes when the thumb hole is moved and the distance between your thumb and your ring finger increases automatically. So physically, it’s impossible to have an offset thumb.

But many very good bowlers and drillers not only believe in the offset thumb; they stand by it.

An offset of something like 1/4″ to the left has been reported to result in a cleaner and stronger release as well as a stronger grip. The thumb can also be offset to the right side, which takes away some of the release strength but can help with release extension.

So who’s right? Fortunately, there may be some common ground to the discussion.

Drilling a thumb hole offset does undoubtedly change the lateral pitches of your fingers. It also changes your center line, defined as the line that passes through the middle of the bridge and the center of the thumb hole. A drilling pattern that approaches the main idea of the offset thumb is the center line transfer, although technically the thumb might not be “offset.” This is likely what most bowlers are talking about when they refer to the offset thumb.

Here’s a good explanation of this centerline transfer (sometimes called shift) layout from the BallReviews forum (credit to user Borincano):

1. Draw the centerline and midline of the persons grip on a ball that fits them very well.
2. Place persons thumb in the ball so that their fingers lay across the finger holes.
3. Take a pencil and draw a line from the center of the finger holes toward the grip midline between your fingers following the angle of the fingers.
You are looking for the angle that the fingers are in reference to their thumb.
4. Now you must take the dimensions form the center point to the two points of the triangle youhave created. These dimensions are what you will use to set up the new ball to be drilled with a CLT Drilling.
5. Create the same lines using the dimensions off the other ball. Also draw a line perpendicularto the new finger centerline. That will help you rotate the grips to the proper angle. The angled line that you have created will be you centerline for drilling the finger holes.
There is many different ways people set up the ball to be drilled. Some drill thumb first others drill fingers first. It doesn’t matter
6. The angled line that you have created by drawing between the fingers becomes the new centerline for drilling the fingers. Rotate the ball so that the new centerline is straight up anddown when the ball is in the jig. Set your pitches, line-up the bit to your lines and punch the hole.
7. Repeat step 6. For the other finger.
8. Rotate grips to be parallel to the line you drew in step 5.
This grip will help the hand lay a little flatter on the ball and to most people it feels more comfortable.”

The dimensions of your own hand are the most crucial factor in deciding if an offset thumb (or center line transfer) are right for you.

There can also be much simpler factors at play that might make a difference. For example, whether your thumb slug/hole is oval or round. If it’s oval, a round hole will probably make things easier.

What do you think about the offset thumb in bowling?