r/Damnthatsinteresting • u/Joanna_Valdes • 8d ago

Bowler's thumb gets stuck in his bowling ball (SFW) Video

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u/BukkitCrab 8d ago edited 8d ago

It's not his actual thumb, it's a piece of bowling equipment called an 'interchangeable thumb' used to customize the depth shape of the thumb hole on a bowling ball.

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u/ecafsub 8d ago edited 8d ago

It does not change the depth of the thumb hole. It’s used to change the shape and diameter.

Finger and thumb holes are drilled to specific depths and diameters. Most custom balls have both thumb and fingertip inserts, being standardized at about 1” OD which makes it dead-simple: slap a 1” bit in the press and start drilling. Obviously there are rare cases where that’s not big enough, but most thumbs and fingers will fit a 1” hole with room to spare. The inserts are used to fill the space. Fingertip inserts are generally a lot softer than the ball resin/urethane while thumb inserts are harder and smoother plastic for better release.

The inserts are selected for finger fit and can be sanded for more precise fits, and are glued into the holes with CA. They are easily replaced. The CA will eventually fail, which is likely what happened.

Source: I’ve drilled hundreds of custom bowling balls.

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u/NeuroticNinett 8d ago

Question about custom bowling ball: Do you need a custom one if you lack fingers, or does a standard one suffice?

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u/Trappedbirdcage 7d ago

If not doing so competitively, I've been to a few bowling alleys that had ramps where you put the ball at the top and push it down. Mainly used for kids but I've seen disabled and older folks use them too.