I was constantly having trouble with the blade clamps on my WEN scroll saw either slipping or completely coming loose when cutting. The original knobs that came on the saw broke within the first couple weeks because I had to "over tighten" just to keep the blades from slipping. I tried roughing the clamping area of the clamps with sandpaper and that helped some but again, the slipping returned. Eventually, having to tightened the clamps so much to try to get them to hold, the threads of the clamp would strip. I started using a regular bolt and a nut driver to tighten the clamps. I made knobs but trying to tighten them by hand was no sufficient enough to hold.
The original blade clamps use a M4-.07 bolt/thread. I drilled and tapped a clamp with a #10-24 and made another knob. So far it has been working fine. The coarser thread tightens faster and you don't have to turn and turn and turn to get the clamp to close onto the blade. Clamps can be purchased through WEN for about $5 each. I've ordered a half dozen and will use them until I start having problems with slippage. Then I'll drill and tap to uses with the larger, coarser thread.
Hope this helps some of the WEN users. My goal is to upgrade saws sometime in the future but for now, this will have to do.