06-23-2016, 05:09 PM
One reason a 6 jaw seems to hold better is that there is more surface contact with 6 jaws than 3. 3 jaw chuck jaws are usually a bit wider than a 6 but they don't have as much metal contacting the work piece as the 3. I will say though that all things being equal a 3 jaw chuck seems to have a little more rigidity than the 6 jaw scroll chuck I have. If the job calls for extra rigidity and holding power it's very hard to beat a beefy 4 jaw with some brass or copper shims between the jaw and workpiece.