HF 8x12 Lathe - Proper method to tighten a 3 jaw chuck

[gorlosky]

I had an eye opener when I was setting up my new HF 8x12 Lathe. I lined up the chuck and tail stock with dead centers and only had to adjust the tail stock just a little bit horizontally and felt pretty good about that. Well I chuck up a piece of steel and trimmed it down and then flipped it around and chucked it up and WOW it is .007 out of round. So I started checking and the spindle is about .001 minus out, and the chuck body is another .003 plus out, so I loosen the chuck back bolts and worked the high spot and re-tightened and now down to .002 minus. BUT when I tighten the 3 jaw chuck on a true round piece like a 1/2 inch drill bit, it can vary from .002 to .007 out of round. I though maybe one jaw was high, but after chucking a 1 1/2 , 1/2 and 1/4 true round objects, that there was no consistent jaw that was high.
Do I need to debur the teeth of the jaws and the worm gears ?
Do I need to use a tightening method like torquing a head, slowly round and round (since there are only 3 places to insert the chuck wrench) ?
Do I need to use a dial indicator and tighten opposite or same side ?
Thanks

 

[darkzero]

Never a bad idea to open up a chuck & deburr/clean, in fact that's the first thing I do with any asian import chuck I get. After that try checking the runout again with an endmill or reamer (on the shank). Guage pins will also work. Some people use drill rod but a ground surface is much better. I use Thomson linear shafts that were suggeted by an experienced machinist on another forum.

Also when chucking something up, if one of the pinions aren't marked, choose one & always use that same pinion when tightening. Loosening doesn't really matter.

 

[Walltoddj]

Always be sure to clean the spindle and face of chips or any foreign matter that will cause it to not locate properly. Do the same on the chuck surfaces I'd advise you not to use air gun it tends to blow chips into unwanted places. Once you get the chuck to locate the way you want there is usually a spot or mark on the spindle mark the chuck the same so you can get it to the same place each time you install it. Hope that helps I learned that years ago and it's served me well.

Todd

 

[gorlosky]

Found some diagrams and tore it completely down. Many areas had burrs, not too dirty though. Small files worked good for the behind the jaw grooves on the chuck. Scroll was a tad tight but came out with patience. I think this will make a big difference in feel if not alignment. Also smoothed the head and tail of the scroll for smoother engagement.