Lately I have been working on some chucks that came with a Hendey lathe I purchased. It came with 2-3 jaw and 2-4 jaw chucks. All of them were rusty. Tonight was the first time I took a close look at the 8" 4 jaw. It was just an extra chuck the fella had around and he gave it to me along with a backplate that he thought I might be able to use with it. I set it on my bench to take it apart and quickly realized that it wasn't just an independent 4 jaw. It is, but its also a scroll chuck. I've never had a 4 jaw scroll chuck. I always pictured something similar to a 3 jaw with one extra jaw...and all of the same runout problems.