One was included when I got my old Grizzly lathe, but I'd never had a need to use it, so far all my work has been cylindrical. But my current project required me to drill and thread a 1/2-14 pipe thread in a rectangular piece of aluminum for an HPA bottle. So I drag out the old 4 jaw, and discover I can't even turn some of the adjusting screws!
You know that oft-repeated phrase, cheap Chinese crap? Well, this chuck is the definition. That said, after some hammer and chisel work (not really), I was able to get things turning more or less freely, and mounted it on my lathe. And that's when the fun really began!
The piece I'm working on is 1" thick by 2" wide by 3" long, and the edge of the hole is about 1/4" from one end in the 1" face. The slots in the chuck are about 1 1/8" wide, that just added to the challenge. Took me a LOONNGG time to get it dialed in, and I gave up in disgust a couple of times. But the alternative was to order and buy a boring head for my mill and a $50 tap, so I kept at it.
All told, this was a major PITA, but it was also an important learning experience. I learned that I need a new 4 jaw chuck , and I also learned that an operation like this needs to be on the lathe from start to finish. I initially bored an 11/16" hole on my mill, that turned out to be a mistake, because it made it impossible to use the usual methods for dialing something like this in.
Bottom line, I overcame the obstacles and accomplished what I set out to do, and it came out pretty well, even if I do say so myself . But it really was an exercise in frustration, and really points up some of the issues of trying to learn machining solely via books and the Internet. Of course, it also shows that it can be done, so three cheers for the Internet! BTW, if anyone has any slick tricks for setting up rectangular work in a 4 jaw, I'm all ears (eyes?)! Later.
I'm not sure that I understand what the problem was with the 4 jaw, it just takes time and patience unless you do it all the time. Some guys will use two chuck wrenches, extra one for the opposing side, so they can loosen one side while tightening and reading the other. Get two sides close, then do the other two opposing sides, then iterate to your hearts content. Square stock you need to read the minimum, i.e., rock the chuck and get the lowest reading at the middle of that side, if you aren't in the middle of the surface, you can't get a reliable reading. Solid support and gentle handling of your dial indicator is important too.
You might check the mrpete site to see if he has any video about the 4 jaw; http://www.youtube.com/user/mrpete222