C3 Mini Lathe Bearing Change

1.Start by disconnecting the machine from the mains supply. Remove chuck

guard, chuck, gear cover and gear train.

(Note: It is not necessary to remove the leadscrew as shown in the picture -

these photos were taken during a complete strip-down of the machine during it's

initial preparation for a customer)

2.Remove belt and layshaft gear

3.Remove the two C-nuts, gear, key, plastic spacer and plastic bearing cover

from spindle.

4.Remove the gear cover support bracket and undo the control box but don't

disconnect it

5. Undo the two screws holding the spindle speed sensor and note how the

timing wheel fits between the forks of the sensor (some C3 variants are not

fitted with a spindle speed display)

6. Working through the holes in the spindle flange, remove the 3 screws from

the front bearing cover

7. Remove the spindle from the headstock using a puller. The diagram shows a

simple to construct puller made with bits from the scrap box.

8. Remove the plastic spacer and key then extract the front bearing from the

spindle using a press/mallet

9. Clean everything thoroughly, replace the bearing cover on the spindle and

press on the new bearing inner being careful to press on the bearing race and

not the cage! An 8" length of steel tube is handy here but ensure the bore is greater than 30mm to clear the spindle and the O.D. no more than 40mm to

clear the bearing cage.

10. Refit the spacer and key to the spindle

11. Extract the rear bearing from the case

12. Press or tap into place the new front and rear bearing outer races

13. To compensate for the wider taper roller bearings it is necessary to make a

new plastic spacer (approx. 0.105" wide) with keyway to fit the spindle between

the timing wheel and gears.

Trial fit the new spacer and adjust as required - the spindle speed timing disk

must not foul the pickup and the gears must mesh correctly

14. Grease front bearing and insert spindle into headstock locating keyed disk,

spacers and gears on the key

15. Fit the rear plastic spacer having first modified it by turning a smaller

diameter step at one end so it clears the bearing cage

16. Grease the new rear bearing and pull it into place using the C-nut, gear and

plastic spacer

17. Temporarily fit the belt cover and check tumbler reverse gear alignment -

they probably won't align because the black plastic spacer is now too long

18. Shorten the black plastic spacer as required

19. Final adjust the C-nuts using two C-spanners to remove free play and pre-

load the bearings

20. Re-fit the drive pulley, belt and belt cover complete with tumbler reverse

21. Re-fit gear train, gear cover and chuck.

22. Re-fit the spindle speed sensor (checking again that it clears the timing

disk!) and re-fit the control box.

Providing you have no bits left over (except the old ball bearings!) and

everything is tightened and adjusted correctly, your lathe is now ready to use.