I have a Woodriver/Quansheng #4 plane which is a fine tool in most respects, but it has been driving me insane with annoyingly sliding lever cap. When retracting the blade, the cap moves with it; when projecting the blade it doesn't come back with it. After just a few back and forth adjustments the cap loses tension and you have to pop it off, put it back, readjust (but not too much because it will become loose again!). Tried polishing what should glide and roughing up what shouldn't, to no avail.
I decided to fix it properly (but first I quickly ran down to LV to get a custom 4 1/2, because after fixing it there would be fewer excuses for a new plane).
To fix it, I just made it a little more like what LV does on all their bench planes (and I suspect some other makers too). Use a 1/2" bit in drill press to create countersink in the cap in the position where the screw sits. Put the screw in the drill and apply a file to it to create a bevel. Presto! The cap now stays put. Caution: don't go too far with this because the screw will now have to go deeper to get the same tension, and you will soon bottom it out in the screw hole and have to shorten the screw. When done as in this picture, I only have about 1/8 turn left from where I like how tight it is. Not easy to make it pretty without a milling machine but at least the cap is not plated and when screw is on my job is not visible.
lever-cap.jpg
I'm keeping the LV 4 1/2 though. Tools may enter. None may leave.