Sieg C3 Installation instructions

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A picture story book to help you dismantle and

reassemble your Sieg C3 Mini-Lathe

Arc Euro Trade Ltd.

10 Archdale Street, Syston, Leicester, LE7 1NA.

Web: www.arceurotrade.co.uk Phone: 0116 269 5693.

C3 Mini-Lathe

Dismantling and

Reassembly Guide

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The Sieg C3 Mini Lathe is currently one of the most popular small

lathes available to model engineers today.

The C3 has a swing of 180mm (90mm centre height) and is

350mm between centres. The spindle has a through bore of

20mm and an MT3 taper whilst the camlock tailstock taper is

MT2. The standard 80mm 3 jaw self centring chuck is mounted

directly to the spindle ﬂange which will also accommodate an

80mm 4 jaw independent chuck, an ER25 collet chuck or an

ER32 collet chuck directly on it’s ø55mm register. A larger 100mm

chuck may be ﬁtted using one of our C3 (adaptor) backplates, but

we do not recommend the use of a chuck larger than 100mm.

Power is provided by a 350w brushed DC motor which is

electronically controlled to give a speed range of 100-3000 rpm

with the aid of a 2 speed gearbox. The Sieg C3 is also ﬁtted

with a spindle speed display and is available in both metric and

imperial options.

This picture story guide is designed to help you dismantle,

reassemble, lubricate and make the proper adjustments to your

lathe.

Before dismantling your C3 mini lathe, you should read through

the entire guide and assess that you have the required equipment

and skills to complete the task. For instance, some operations

require the use of a lathe and you can’t use your C3 if its all in

bits!

Although not expressly stated at each stage in this guide, every

part is thoroughly cleaned in a parafﬁn type solvent before

reassembly.

For lubrication, we recommend Molyslip HSB grease (ARC code:

170-100-10300), and a good quality lubricating oil such as Rock

Oil HLP 32 Hydraulic Oil (ARC code: 170-150-00400). We do not

recommend using automotive engine oil or 3-in-1 oil.

Please note that Sieg also manufacture the C2 and C2A mini

lathes which are smaller variations of the C3 and will have some

construction differences. There are also other factories in China

making mini lathes similar to the C3 so these will be different

again.

1. The lathe out of the box and we are ready to start work. 2. Remove the chuck guard and rear splash guard.

3. Remove the tailstock. 4. Remove the chuck.

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5. Remove the tool post and remove the indexing plunger and spring and keep in a safe place.

PLEASE READ THIS FIRST

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10. Remove compound slide and gib strip. 11. Unscrew the leadscrew from the compound slide base.

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12. Remove the compound slide base.

6. Remove the screw securing the compound slide handle. Remove handle and spacer.

7. Tap compound slide along with a soft mallet to remove micrometer dial and friction clip.

8. Remove the leadscrew end plate.

9. Slacken the gib adjusting screws.

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13. Wind the cross slide off the lead screw.

14. Slacken the gib adjusting screws.

15. Pull off the cross slide assembly.

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16. Remove the screw securing the cross slide handle. Remove handle and spacer.

17. Remove the leadscrew end plate and leadscrew.

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18. Remove the gear cover.

19. Undo and remove the ﬁnal drive gear.

20. Undo and remove the gear quadrant.

21. Undo the ﬁxing screws on either side...

...and remove the transfer gear carrier.

22. Undo and remove the tumbler reverse arm.

and

remove

the

transfer

gear

carrier

22.

ndo and remove the tumbler reverse arm.

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31. Remove the gear cover support

bracket.

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30. Remove the rack from the front of the bed.

28. Undo the screws securing the apron and remove. 29. Slacken the saddle adjusting screws and slide the saddle off the end of the bed.

26. At the tailstock end, removed the leadscrew carrier bracket. 27. Draw out the leadscrew.

24. Remove the spacer and key from

the main leadscrew.

25. Remove the leadscrew carrier

bracket.

23. Remove the drive belt cover/backplate.

Dismantling the spindle

Steps 31 to 81 include a bearing change from standard ball raced bearings to taper roller

bearings. Switching to taper roller bearings will improve the machining accuracies and ﬁnish.

Since in many cases, taper roller bearings are not an essential upgrade, and because

you will need access to a hydraulic press and bearing separator you may wish to keep the

standard ball races and skip forward to step 82.

32. Remove 4 screws securing the control panel and lay to one side.

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39. Remove the motor cover. 40. Slacken the two drive belt adjusting screws.

41. Slacken the motor mount pivot screws and remove the drive belt. 42. Undo the motor mount pivot screws enough to remove the motor.

35. Disconnect K3 and K4 safety cut-out wires from the control board. 36. Disconnect the motor wires.

37. Disconnect the mains supply leads from the emergency stop switch. 38. Put the control box to one side.

33. Undo two screws and remove the speed display pickup. 34. Disconnect the three earth wires.

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51. Press spindle out of head. 52. Remove spacer and key.

49. Using a hole in the spindle ﬂange for

access to the 3 ﬁxing screws, remove the

front bearing cover.

50. Undo and remove the three screws ﬁxing the head casting to the bed and remove the head.

43. Remove the chuck guard carrier spindle etc. 44. Remove circlip & pull off drive pulley. 45.

Using two C spanners, unlock & remove spindle nuts.

46. Remove Spindle Gear. 47. Remove key and spacer. 48. Remove the spindle rear bearing cover.

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61. The new bearing in place.

55. Press or drift-out rear bearing and remove

the large white plastic spacer.

58. Apply light coating of grease to gears and

gear change linkage.

63. Make and ﬁt a new 0.190” (4.8mm) spacer between the gear and speed

encoder disk inside headstock.

57. Press or drift-in new 30206 taper roller outer

races to both front and rear of headstock.

60. Reﬁt front bearing cover to spindle and press on

new 30206 taper roller bearing inner

64. Reﬁt the key, the original spacer + the small 0.110” (2.8mm)

thick spacer (the original small spacer reduced in thickness)

to the spindle and grease the bearing.

62. This picture shows the complete sequence of parts loosely assembled on the spindle.

Gaps are left to clearly show the parts. There will be no gaps when assembled in the

head. *Note the outer spacers require a shoulder turning to clear the bearing cage.

56. Remove the small white plastic spacer

through the speed display pickup hole.

Reduce the thickness of this spacer to

0.110” (2.8mm) before reﬁtting later.

59. Reﬁt headstock to bed making sure

mating faces are clean and tighten down.

53. Press or pull off bearing and remove bearing cover from spindle.

If the bearing is tight to remove, polish the spindle to make the bearing a Push Fit

otherwise you will not be able to preload the taper roller bearings accurately.

54. Polish the spindle and test the ﬁt by using one of

the old bearings (if not damaged).

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65. Assemble spindle aligning keyways in spacer, speed

encoder and gears. 67. Grease and ﬁt new 30206 bearing.

70. Lubricate threads and ﬁt C nuts - hand tight only.

73. Secure front bearing cover.

76. Thread mains cable through but

do not ﬁt motor cover yet.

69. Fit metal drive gear.

72. Fit plastic drive pulley, secure with circlip.

78. Reconnect all the wires to the control box.

75. Reﬁt the drive belt and adjust tension. If you cannot twist the belt

through 90° quite easily, the tension is probably too tight.

66. Fit rear spacer with shoulder facing out.

68. Fit the plastic rear spacer previously

modiﬁed in step 62 and the key.

71. Fit rear plastic bearing cover.

77. Reﬁt the cable protector.

74. Reﬁt the motor onto it’s pivot screws.

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79. Check the speed encoder disk aligns with the pick-up and ﬁt. 80. Reﬁt the chuck guard assembly.

81. Adjust the bearings for “slight drag” and pinch up the C nuts for the moment. Following the Start Up Procedure on page 18, run the spindle to warm

it up and settle the grease. Check and adjust the preload again. Lock the C nuts when the preload appears to be OK. Take care not to overdo the

preload as this could overheat and damage the bearings.

82. Check the drive belt is running on the centre of the pulley. If not, then adjust the motor’s lateral position with the motor pivot screws.

83. Check the drive belt tension again.

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89. Place the saddle on the bed and

check to see how it sits.

90. If it rocks, blue the bed and slide

the saddle up and down to ﬁnd the high

spots.

91. Scrape, ﬁle or stone down the high

spots until the saddle sits ﬂat on the bed.

87. Drill and tap the ﬁxing holes deeper if necessary. 88. Final ﬁt rack making sure it seats properly in the corner.

84. Scrape any paint off the bed shears. 86. If necessary, radius top rear edge of

the rack and trial ﬁt again.

85. Trial ﬁt rack to check if it seats or rocks.

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