Trouble centering square stock in 4 jaw chuck
Im new to this and really need to get this done for a project. Any help would be much appreciated.
I just cant seem to center a piece of square stock in my lathe using any of the videos or written instructions ive seen. It just doesn't seem to work when I try it. Is there a decent diagram around that illustrates the steps to this?
Thanks in advance!
How to: Centering square stock in 4 jaw chuck
First, make sure your chuck is running true. Indicate and adjust as needed. A lot depends on how "clean" your material is, meaning not damaged, etc. Depending on your application and material condition, you may be able to just indicate the corners. Ideally, for concentricity and follow up mill work, you want to indicate the flats. Set up your indicator on the cross slide so that it can be moved onto and off of the material using the Z axis handle with vertical aligned at spindle center line (Y axis zero). Place your material in the check jaws and snug down equally. Measuring jaw position with a scale or depth rod of a caliper works fine for this. You should be able to get to within 0.020 just with this method alone. Then rotate spindle and place flat vertical. Mark this as #1. Move indicator onto flat as near chuck jaw as is reasonable. Rock flat back and forth and find smallest indicator reading and move indicator bezel to "0". Move indicator off of material and rotate spindle 180 degrees to side #3. Move indicator back onto material and rock again to find smallest reading and note difference from "0". Adjust jaws for sides #1 and #3 to 1/2 the total, moving indicator on and off of material as needed to rotate by loosening #1 and tightening #3 or vice versa as needed. When you are comfortable that the material has been centered in the chuck along the X axis, snug and recheck a final time and repeat process on sides #2 and #4. After centering across jaws for #2 and #4, recheck #1 and #3. Readjust if needed. For final tightening, it is important to tighten each jaw very sightly and in order while watching indicator for addition deflection while rotating to each side around the material. by doing this, you should be able to get it very tight without losing your center during this process. If you have material that is sticking out of the chuck jaws more than 2 times the material size, you will probably want to check the end of the material on the flats for run out. Bump material with soft face or dead blow hammer to adjust. Recheck near chuck and retighten as needed. A well practiced and skilled machinist can usually do this process in about as much time as it takes to read this instructions. You milage may vary.