If you've bent a driveshaft on one of your rigs, bending them back is an easy way to save some money. You can use a hammer but it's less than ideal, and there are straighteners out there but they cost a pretty penny. The best method I've found uses a bench vice and 3 long bolts. However, keeping them all balanced can be a pain with only two hands.
Introducing, the Driveshaft Straightening Jig!
Features variable bolt positioning for various size driveshafts.
Just grab some large bolts (mine are around 7mm diameter) and some matching nuts, drop them into the appropriate spaces, float the jig over your vice, and crank away until it's (mostly) straight again.
I recommend printing out of TPU so just in case the jig gets wedged in the vice, it doesn't explode. Doesn't need much in terms of material, I'd go with 15-20% infill and 3 walls for some protection, more if you print in a rigid material.
Check out a video of it in action:
The author marked this model as their own original creation.