CNC hold-down clamp

This is a remix of https://www.thingiverse.com/thing:2427778 for my small 3018 CNC. Here are the changes:

- Scaled up x1.25
- Slot instead of a round hole for a larger M6 bolt
- Rounded back for better pressure distribution
- Larger "teeth"

Printed on the side with or without supports, 5 perimeters, 4 bottom and top layers.

Added v2 model with smaller teeth.