I bought a 7x12 Chinese mini lathe a few months ago. Lately there is a loud clunking in the headstock, I determined it to be the belt slipping so I pulled it apart and found it wasn't tracking quite perfect and might have been too loose, so I shimmed it up a bit with a washer I made out of a credit card tightened it just now, doesn't seem to be slipping anymore. Does anyone know how much tension I should have. Does anyone have any experience with the 3:1 reduction upgrade with metal gears, does it effect threading with the change gears can someone please help me that has personal experience with this....thanks!
Welcome to the forum 00harleydyna . You will learn a lot here. We have the best group of members on the planet. We love questions.
Go to the little machine shop and get the mini lathe generic users guide under the learning center tab:
http://www.littlemachineshop.com/default.php
The following is the belt adjustment procedure from that guide:
Drive Belt
The drive belt needs to be aligned correctly or it will wear on one side or the
other.
15
To adjust the drive belt:
1. Unplug the power cord.
2. Remove the motor cover from the back of the lathe.
3. Remove the change gear cover.
4. Remove the control box from the front of the lathe, but do not disconnect
any wires.
5. Loosen all the lock nuts on the front of the lathe.
6. Back off the top and bottom set screws a couple turns.
7. Make sure that nothing will get into the change gear drive.
8. Make sure the control box is in a safe but accessible position.
9. Plug in the power cord.
10. Reach around to the back of the lathe and hold the motor.
11. Turn the motor on at slow speed.
12. While the motor is running, move the motor to a position where the belt has
sufficient tension and does not rub either side of the pulley.
13. Tighten the nuts on the two studs that are aligned horizontally.
14. Snug the setscrews that are aligned vertically.
15. Turn off the motor.
16. Tighten the lock nuts.
17. Replace the control box.
18. Replace the change gear cover.
19. Replace the motor cover.
My belt has a slight bow (1/8" to 3/16")when pressed on with light finger pressure with the motor not running. You don't want it too tight. I use the 3 to 1 reduction pulley and belt set up available on eBay. Is that what you are referring to? I have all metal gears in the spindle head and all metal change gears. Everything works great. There is a reduction in speeds when using the 3 to 1 pulley/belt set up but the torque is a lot better. I highly recommend the metal gears and 3 to 1 pulley/belt upgrade. Threading remains exactly the same as it was. The reduction is between the motor and spindle. The change gears are driven by the spindle so everything stays in sync. The change gear chart remains the same.
Here is an online change gear calculator that I like:
http://www.cgtk.co.uk/metalwork/reference/changegears
Roy
