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I have been watching a few of the YouTube machinists and it seems that the 4 jaw chuck is becoming all the rage. Now, I understand the need for one when offsetting or working with square stock, however, if your 3 jaw is accurate, what's the advantage of the 4 jaw on round stock. I just tested my 3 jaw with a. 750" gage pin and it shows less than a thou TIR. I chucked up a piece of 1" round bar and took one. 050" cut and then a .010" cut and checked the runout and still less than .001" . To be honest I doubt that if I had indicated it in the 4 jaw I would get much better results. This is just one of those "hmmmm" thoughts and questions and just wanted to get you guys take on it. Cletus
Quote from: Tennessee Whiskey on November 06, 2016, 07:38:25 PMI have been watching a few of the YouTube machinists and it seems that the 4 jaw chuck is becoming all the rage. Now, I understand the need for one when offsetting or working with square stock, however, if your 3 jaw is accurate, what's the advantage of the 4 jaw on round stock. I just tested my 3 jaw with a. 750" gage pin and it shows less than a thou TIR. I chucked up a piece of 1" round bar and took one. 050" cut and then a .010" cut and checked the runout and still less than .001" . To be honest I doubt that if I had indicated it in the 4 jaw I would get much better results. This is just one of those "hmmmm" thoughts and questions and just wanted to get you guys take on it. CletusYou are very fortunate to have a three jaw that will center that well over a range of diameters. If you really want to check it do about 6 different diameters over the range of the chuck. If they all come in that close, then set that chuck aside in a special, protected place, and use it only for those jobs where you need that accuracy. Then go buy another chuck for normal work...Pete
I chucked up a piece of 1" round bar and took one. 050" cut and then a .010" cut and checked the runout and still less than .001"
Both my 5C and 3-jaw are Bison Set-Tru. After reading this, I went to the shop and checked them since I hadn't done so in months. Both bang on ("bang on" is defined as less than .001 TIR). One you figure out the procedure for clocking the Bisons (the adjustment screws are in an asymmetrical pattern???) it takes just a few minutes and they do seem to hold the setting.As Kirk said, as long as the stock is greater than the runout....Vern