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Centre round bar in a 4 jaw chuck

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Anzaniste:

APOLOGIES FOR LACK OF PHOTOS BUT MY NEW LATHE DOES NOT HAVE A FOUR JAW CHUCK MOUNTED YET. :(


I used tO do it like that but some one told me a much quicker way.


Initially you  ignore the positions of the jaws until later .

1) Center closely by eyeball as described in the original method in this thread.

2) Mount the dial gauge on the cross slide  so the face is looking up. (I have mounted a dial gauge on a piece of square bar which I put into the tool holder)

3) Wind the cross slide in until the plunger touches the work piece.

4) Wind in until the needle is pointing to your right. Then the needle will move towards you if the work piece eccentricity causes it to move towards you and vice versa. I find this helpful even though not essential.

5) Revolve the chuck watching the needle  travel making a mental note of the maximum  and minimum readings and count the divisions between min and max, divide by two and set the bezel pointer at the mid point between the max and min readings  .  ( I  find it less confusing if I move the bezel pointer to either the max or the min point and work out the mid point from there)

Now is the time to look at the jaws.

6) Rotate the chuck til one pair of jaws is at 9 o'clock and three o'clock.

7) Adjust the jaws until the dial needle corresponds with the bezel pointer. It is a fantastic speeder up of this process if you have a  a chuck key for each jaw. Additionally if the dial gauge needle is pointing to the right the needle follows the work piece so to speak and is therefore more intuitive for the beginner.

8)  Repeat for the other pair of jaws.

9)  Bingo!you will find your work piece centalised perfectly. ( You might have to do a small amount of careful adjustment as you tighten up to working tightness on the chuck jaws.


I can centre in the 4 jaw in a tehth of the time it took me to write this.

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