How to True a Lathe Chuck Jaw
When you are using a lathe, you may find that the lathe chuck jaw sometimes moves out of the line you have set. In order to get the perfect cut from your lathe, you will need to adjust the chuck jaw back into true, so that you can get a great cut from it without having to go to too much trouble. You can true your lathe chuck without a great deal of effort, using just a simple pieces of wood and some basic home improvement tools which you will find around your house. This project can be completed in a short space of time, and you will not need any assistance.
Step 1 - Take Stock
In order to establish whether your lathe chuck is out of true, you will need to take a piece of stock wood, perhaps one which you have used previously when cutting, and place it in the jaws of the chuck. The stock should not be any larger than around one inch in diameter, and you should leave four inches or so emerging from the chuck. This size means that you can examine the stock without having to remove it every time you want to examine the chuck.
Step 2 - Make a Cut
You should now take the edge of your stock, and take your toolbit edge. This needs to be as sharp as you can get it, and with a very small tip, so that you can cut across without leaving too large a mark. With the chuck held tightly, make a small cut on your stock. Then, using the lathe, make another small cut on the sides of the chuck, lower than the first.
Step 3 - Measure the Marks
You will now have a stock with two small cuts, one from the toolbit, and the other from the lathe. Measure the cuts on the stock using a tape measure, and examine whether they are parallel. If your lathe cut is at a different angle from the control cut, then this shows the angle which your chuck needs to be altered back to true. You should then take your oil, and a screwdriver, and move the jaw slowly backwards or forwards, depending upon the angle of the lathe cut.
Step 4 - Finishing
Once you have adjusted your chuck, replace the stock back into the jaws, and make another cut with the lathe. Compare this with the control cut again, and look to see whether the two cuts are now parallel, or whether you need to make further adjustments with your screwdriver. You can also check how well the chuck is holding the stock by examining the amount of wobble produced during the lathe work (if there is too much wobbling, you may have to tighten the jaw up, as well as move it around). Once the lathe line is perfectly straight, your chuck jaw is back into true.