Now I tried holding the blade with a pair of slip-joint pliers and couldn't get the bolt to budge. I got a hefty washer on there, threaded the bolt back on, tightened the you-know-what out of it, and the difference is obvious without even running it - before, I could hold the blade with my fingers and spin the shaft with a wrench. So it's a problem with the blade thickness. I got the bolt off (yes, reverse thread) and yes, the diamond knockout is knocked out. Any help would be appreciated!Д®dit: Thank you all for your suggestions!

This scares me, but I really want to be able to fix ths so I can get back to cutting. No jerk or bounce-back, the shaft spins but the blade is obviously not tight to the shaft.

If there's no real drag it cuts fine, but the least thing makes the blade just stop. We replaced the blade for something newer, as I've got some cabinetry to tackle - but neither he nor I can get the blade to tighten down. It's an old solid metal case, the thing weighs like three times the Ryobi direct drive, but when it's running, it doesn't feel like anything at all! I love the darned thing. I was having so much trouble controlling a direct drive circular saw due to the gyroscopic twist when starting it up, my 'adopted brother' found me this wonderful worm drive Skilsaw. I'm on a farm, and I'm a little person learning to do big work.

Skilsaw model 77 hb599859