How do DVDs get cracked in the mail? I thought it obvious until I tried to crack some.

Factual Questions
1

I occasionally get a DVD in the mail that is cracked from the center hole to the outside. I just assumed it was mishandling somewhere along the way.

Then - yesterday I was taking out some trash DVDs and a whim decided to crack one. I attempted several times with different DVDs and I can damage them but never succeeded in cracking one from the center hole to the outside.

Can you explain how the cracks happen?

2

Temperature differential, maybe? Part of the CD is hot, and another part is cold, causing internal stresses. If the outer part were cold and the inner part hot, the outer part would be being stretched circumferentially. A small nick might turn into a crack, which then propagates to the center.

3

Maybe… They get stacked with a sharp edge running across the middle - you know, edge of a book or other solid parcel. Add a soft weight above like a bunch of papers, so it’s being bent across the edge; take it on a boncing ride over inner city roads, a few potholes… and it will crack along that edge.

4

I’m guessing hold it by the outer edge, insert and remove it from a laptop drive a few times.

5

It was my understanding that they got cracked while they were running through the postal machines. Allegedly Netflix envelopes tend to jam equipment. Is The Post Office About To Kill Netflix's Business Model? | Techdirt
Netflix envelopes anger Postmaster, Postal Service balks

6

Yes, the sorting machines run the mail through a circuitous path which includes a number of fairly tight radius bends. There are also devices called diverters which alter the path of individual envelopes as they travel through the machine, so they end up in the correct stack. They kind of slap the envelope to accomplish that.

I worked on a project designing and building automated testing fixtures for the then-new generation of postal sorting machines in the mid 90’s. The prime contractor I was subcontracting to was the most vicious, unprincipled, evil company I have ever encountered. I laughed and laughed when the the USPS canceled their contract right after they finally got their mass production facility online. (conveyors and the whole bit) It sucked for the workers, but my god they were treated like shit for the privilege of a paycheck. Management was strictly a matter of threats, intimidation, and retaliation.