I think my answer is the same, RAPID temperature change.  Also, I think that it's the same thing as with vehicles, some are deemed as "lemons".  I think the same thing applies to bowling balls, just the variance in different pours.  I could never prove that but that would be my hypothesis.

GetOffMe10Pin

 

-"If you want to make enemies, try to change something." - Woodrow Wilson

Other than severe treatment, I have no idea.  I've had 3 balls crack.  The first was a Storm (urethane) Thunderflash.  The cover was at least 5/8" thick.  It wasn't used a ton, but the ball did crack through the plug work.  Urethane doesn't absorb much oil, so the "removing oil from the causing brittleness" doesn't apply even if it had been de-oiled, which it hadn't.  The other two were 900 Global Creatures.  The first looked like the core wasn't put in the mold correctly when they poured the cover.  Near the fingers, the cover was very thin, but the bottom of the ball had a much thicker cover.  The second was I found two weeks ago.  I was getting my equipment ready for a tournament and found the ball cracked from the top of my middle finger around the ball to the bottom of the thumb slug.  I don't use finger grips, so glue isn't the problem.  Everything has bevel so that's not it either.  Neither ball was old or had more than 50 games on them, so it's hard to blame oil or abuse.  Everything is kept on my ball rack or the carpet beside in my den.  A little "spider webbing" can be ignored or fixed, but a crack from end to end is a killer.  I just don't know.

I just lost my 2nd RSX on Sunday. Granted both balls are 07 balls but they cracked about 18 months apart. From what I can see it almost looks like the filler core is shrinking causing the crack. RSX no.1 is sitting on the mantle since it was my 300 ball and the crack has gone from about an 1/16th of an inch to about 3/8th of an in wide in the last 18 months, so something is still changing even though the ball is in a controlled climate.

I'd suggest 2 other possibilities.

1. Curing, as already mentioned

2. Driller error

 

1. The old Columbia300 San Antonio plant being near desert conditions, seems to have had problems with the curing rate. 900Global seems to have reduced that rate greatly since they took it over after the sale of Columbia to Ebonite. It still happens ocassionally

 

2. Drillers still do lazy or ignorant things, like

- using too much super glue on inserts (it seems tomake the resin coverstock brittle)

- drilling with dull bits, creating too much heat, again making that area of the resin sensitive to cracking.

- not beveling all holes.

- placing the pin too close ot holes (1/2-3/4" seems to be the minimum safe distance, or putting the pin in the center of a hole also seems to be safe.). Putting the pin close to the hole is never a good idea.

 

My guess is two parts.

 

Glue, and temperature.

 

 

The reason I say glue is from something I have observed over the years. I used finger inserts for years and many of those bowling balls did crack out. (starting from the fingers) They were kept in my bedroom or office and only exposed to the elements while going to and from the center. One ball was two years old before drilling, and was barely used before cracking all the way around the ball while sitting on the floor of my bedroom.

 

In 2001 I went away from finger inserts. Since then I have drilled many times more bowling balls then with inserts and only had one crack.(from the thumb, it was a bonanza 2 ball) Nothing else I have owned has ever cracked since going to inserts.

 

My brother still uses inserts, drills far fewer bowling balls and has had several crack. All start at the fingers.

 

Finial thoughts. When gluing inserts and thumb slugs always try and get the glue well below the outer surface(coverstock) of the ball. I think from what I have observed that the glue plays a big part in why so many bowling balls crack, usually around the fingers first. Even glue that says it is suppose to not cause cracking.

 

This is from observing many bowling balls that were not exposed to the elements.

Would the thickness of the covers make a difference? Most balls seems to be pretty "thin-skinned" these days. Has anyone had their LaneMaster balls or other balls with thick, deep coverstocks have cracking issues?