 Welcome to changing gears and setting the backlash. In this video, you'll learn how to make changes to an engine lathe. Drive from the headstock to the gearbox is transmitted through the change or end gear train. Machinists often need to change gears to achieve the desired feed rate or thread pitch. They do this by changing the gear configuration. The number of gear teeth, which is stamped on the gear, determines change gears. Change gear configurations and the corresponding feed and thread pitches are found in the data plates at the front of the headstock. To change gears, begin by properly locking out the electricity to the machine. Open the end guard door. Determine the proper wrench assortment. This is a metric machine, so only use metric wrenches. Adjustable wrenches should never be used. Look at the data plate and establish which gear combination is needed. Collect the needed gears. Some may remain on the machine. Thoroughly inspect and clean each one. Loosen the stud gear hex head screw. Loosen the idle train T-nut. Don't loosen the idler train T-bolt at this time because you want the gears to stay engaged. Loosen the output shaft gear nut. The output provides power to the change gearbox. It's the bottom gear in the train. Remove the two nuts and bolts once they're loose. Remove the stud gear. It's at the head of the gear train and is driven by the spindle gears. Remove the drive gear on the idler shaft. The drive gear is in mesh with the output gear. Remove the spacer that's between the drive gear and the driven gear on the idler shaft. Remove the output gear. And finally, remove the driven gear. It's meshed with the stud gear or the top gear. Now let's look at the other parts that make up the change gear configuration. This is the swing frame, swing frame bolt, T-slide, gear spacer, and the shaft sleeve. To reassemble the gear train, begin by sliding the stud gear in place. Make sure you have the stamped gear tooth numbers showing. Next, hand tighten the stud gear bolt. When reassembling the gear train, make sure to keep your fingers clear of any pinch points between the gears. Rotate the swing frame up before lightly tightening its bolt. Loosen the T-slide bolt. Slide the driven gear into place. Replace the spacer that's between the drive gear and the driven gear on the idler shaft. When you've completed reassembling, all of the gears should be flush with one another. Next, slide the drive gear into place. Replace the T-slide nut and lightly tighten it. Take a double-up piece of paper and place it between the driven gear and the stud gear. Mesh the driven gear with the stud gear by sliding it into place. The backlash between the end gears should be 5 1,000s to 10 1,000s of an inch. A single sheet of paper is approximately 4 1,000s of an inch. So, a double-up piece is around 8 1,000s of an inch, which makes it a great tool for checking the spacing. It's important to maintain the proper amount of backlash between gears. Tighten the T-slide bolt and slide the paper out. Check for any movement between the gears. This movement is called backlash. Place the output gear on the output shaft. Place a new double-up sheet of paper between the driven gear and the stud gear. Hold the driven gear in one hand while loosening the swing frame bolt. Let the driven gear down and gently mesh it with the output gear. Tighten the swing frame bolt and slide the paper out. Check for any movement between the gears. Finish tightening the output shaft gear nut. Tighten the idle-train T-nut and recheck the tightness of the idler-train T-bolt. Tighten the stud gear hex head screw. Check the entire backlash between the gears and make sure all meshed gears are flush to one another. Close the end guard door. Finally, remove the electrical lockout. To check your work, start the machine and turn the spindle on. The gear-train should run smooth. If it's noisy, you may need to adjust the gear-train to avoid damaging the end gears. If the machine is running smoothly, you've correctly changed gears and set the backlash. You can now begin working. You've completed changing gears and setting the backlash.