A common issue which occurs when assembling and disassembling a robot is the head of a screw can become stripped. In other words, the hex socket becomes rounded and the hex key does not have enough grip to loosen the screw. When this happens there are some techniques to help remove the screw.
The Hex Keys can become rounded at the end through repeated use, so when trying to remove a stripped screw it is best to use a new Hex Key or a new Hex Driver from the Performance Tool Kit. There are also commercially available high torque hex keys which are hardened more than a standard hex key. These new tools may grip the stripped head enough to loosen it. A rubber band can also be placed over the stripped screw head before the hex key is inserted to help with the tool’s grip.
Friction between the stripped screw head and the structure it is connecting can be used to loosen the screw. This method involves removing all the other fasteners from the structure and then moving the connected pieces back and forth until the screw loosens.
A rotary cutting tool with a metal cutoff disk can be used to cut a slot across the top of the stripped screw head and then a flathead (slotted) screwdriver can be inserted into the slot to remove the screw. A rotary cutting tool or an angled grinder with a grinding disk can be used to grind off the head of the screw.
The best practice is to not strip a screw in the first place. Although this is not always possible, there are some things which can be done to avoid it. The High Strength Stainless Steel Screws and Star Screws are much less prone to stripping than the black screws which come with many of the kits. Power screwdrivers and T-handled wrenches should be avoided because they apply too much torque to the screw head. Inspect tools frequently and replace if they begin to wear. If a partially stripped screw is successfully removed, discard the screw, do not place it back in with the other screws.
Be cautious around material which has just been cut.
Screws can be purchased at https://www.vexrobotics.com/all-screws.html.
Hex Keys can be purchased at https://www.vexrobotics.com/tools.html.