This clamp detail often breaks. The idea was suggested to me by the author of this model https://www.thingiverse.com/thing:3052609, but having studied in detail, I realized that it would not suit me. Therefore, I made my own version.
There are two versions in the archive for 4 and 6 inch clamps.
See the video for details:
In China such clamps can be bought for a couple of bucks ( https://goo.gl/1zTzuc ), but I wanted to fix the old one.