Everyone has given good advice. I wish to add a slightly different point of view, an addition, not a revision, as they are correct.
As I have arthritis in my whole body, I had to make a tightening knob that was large and did strip the screw. I also did repair it and now am a little more careful when tightening the blades into the holder.
I also have gone to a clamp to hold the blades in position while I feed them into the clamps. I have a cheap long, clothespin type clampt that I use for this. It holds the blade in position while I adjust front to back and vertically to get it better to start.
There are tiny floating grips that can become glazed. Use a very fine sandpaper/diamond file etc.to scuff these hardened pieces up enough to grip better. Be VERY careful to keep them flat while doing this. I had put them into a piece of scrap wood and in my vice to do this. I have machinists vice and use homemade adaptor plates for the wood things I use it for the most. Works as well as most actual woodworking vices.