Great video showing the USPS AFCS 200 sorting machine in action. You can see all of the turns where letters must bend around a 4" spindle.
Commentary from a USPS AFCS operator:
Some Tips and Debunking Myths on Shipping Cards through USPS.
After seeing the post yesterday from a front end postal worker and some misinformation in the comments. I thought I should give you some insight from someone who used to run the machines that process your mail.
Myth - Stamping your mail with "hand sort only", "non-bendable", "do not bend", "non-machinable", or "warning nuclear bomb inside" will cause your mail to be processed differently than normal mail.
Nothing on your envelope is read by a person. Only by going to the post office, paying the non-machinable up charge, and giving them the mail directly will cause your mail to be hand sorted. When the mail arrives at the processing center from the local post offices, the non-machinable mail is in a tote separate from regular mail. It is then put through a relatively slow machine without any bends to cancel and code the mail.
If you don't do this the mail is first run through this machine, AFCS 200. This is the machine I ran. In the back at the start of the video you can see part of the giant purple machine where the letters are first dumped on conveyor belts and staged before being fed into the AFCS.
There is a large eBay
card vendor in my area and we get a few hundred letters a day from them. I always dread it when it comes in and hope it goes down one of the other AFSC. They frequently get jammed and torn. As you can see by the video the mail can be bent around 4" spindle. If your letter can't bend around a Chunky soup can, it won't make it through the machine. If it jams it is removed but I've seen it fall out of the belts and get destroyed. Felt bad to see a play set of [[Sunken Ruins]] destroyed from rubbing against a belt for 3 hours.