I was browsing the interwebs the other day and ran across videos on using a 4 jaw chucks. I thought to myself, although some were ingenious, that these were the most labor intensive and cumbersome ways to center stock in a 4 jaw I have ever seen. Some worked well enough on square stock but did not address out of round, rectangular or irregular shapes so I would like to share with all you hobby guys what I think is a pretty good system.
The first thing needed is to mate the individual jaws to their respective slots. By this I mean number the jaws and slots, I used a Dremel to mark the jaws and a center punch to mark the slots. (see pics 1-4j and 2-4j) The jaws need to stay in the proper slot or the timing gets off.
Next chuck up a piece of round stock, this should be as round and straight as you can find because this is your reference. On a 8” chuck a 3”-4” piece would be ideal but any round stock will work. Indicate the stock as close as you possibly can, the more accuracy in this step cascades down to your actual use. When you have the stock indicated and running straight you are going to mark the jaw screws. These are usually hardened and once marked if they are wrong you may not get a second chance. Grind a notch in all 4 jaw screws in the same quadrant, straight up or down, left or right doesn’t matter as long as all the marks line up. Only one notch per screw. (see pic 3-4j)
Now when you chuck up a piece of stock use the lines on the face of the chuck to get the jaws close and line up notches on the jaw screws. On square stock the notches will all line up, on rectangular stock the opposite jaws will line up. In this case the notch points to about one o’clock. (see pic 4-4j)
I used this on a couple of Cushman 24” chucks and 5 – 10 thousands TIR was not uncommon before reaching for an indicator
.
The first thing needed is to mate the individual jaws to their respective slots. By this I mean number the jaws and slots, I used a Dremel to mark the jaws and a center punch to mark the slots. (see pics 1-4j and 2-4j) The jaws need to stay in the proper slot or the timing gets off.
Next chuck up a piece of round stock, this should be as round and straight as you can find because this is your reference. On a 8” chuck a 3”-4” piece would be ideal but any round stock will work. Indicate the stock as close as you possibly can, the more accuracy in this step cascades down to your actual use. When you have the stock indicated and running straight you are going to mark the jaw screws. These are usually hardened and once marked if they are wrong you may not get a second chance. Grind a notch in all 4 jaw screws in the same quadrant, straight up or down, left or right doesn’t matter as long as all the marks line up. Only one notch per screw. (see pic 3-4j)
Now when you chuck up a piece of stock use the lines on the face of the chuck to get the jaws close and line up notches on the jaw screws. On square stock the notches will all line up, on rectangular stock the opposite jaws will line up. In this case the notch points to about one o’clock. (see pic 4-4j)
I used this on a couple of Cushman 24” chucks and 5 – 10 thousands TIR was not uncommon before reaching for an indicator
.
