Arc Euro Trade SC3 Installation instructions
© Arc Euro Trade Ltd, England 2012
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A picture story book to help you dismantle and
reassemble your Sieg SC3 Mini-Lathe
Arc Euro Trade Ltd.
10 Archdale Street, Syston, Leicester, LE7 1NA.
Web: www.arceurotrade.co.uk Phone: 0116 269 5693.
SC3 Mini-Lathe
Dismantling and
Reassembly Guide
eurotradearc co uk
UNBEATABLE VALUE ENGINEERING PRODUCTS
© Arc Euro Trade Ltd, England 2012
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6. Remove the leadscrew gear. 7. Remove the quadrant.
The Sieg C3 Mini Lathe is currently one of the most popular small
lathes available to model engineers today. The new Sieg SC3 takes
the Mini Lathe to a higher level by employing a powerful 500W
brushless motor and eliminating the 2 speed spindle gearbox.
The SC3 has a swing of 180mm (90mm centre height) and is 400mm
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
ange 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 tted using one of
our C3 (adaptor) backplates, but we do not recommend the use of a
chuck larger than 100mm.
As mentioned earlier, power is provided by a 500w brushless DC
motor which drives the spindle directly via a toothed timing belt and
is electronically controlled to give a speed range of 100-2500 rpm.
The Sieg SC3 is available in both metric and imperial options and
Standard indexable dials are tted as standard to the cross slide and
top slide. The machine is tted with a socket for an optional spindle
speed display and digital readouts are also an extra option.
This picture story guide is designed to help you dismantle,
reassemble, lubricate and make the proper adjustments to your
lathe.
Before dismantling your SC3 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 lathe if its all in bits!
Although not expressly stated at each stage in this guide, every part
is thoroughly cleaned in a paran 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, C2A, SC2 and C3
mini lathes which are all smaller variations of the SC3 and will have
some construction dierences. There are also other factories in
China making mini lathes similar to the C3 so these will be dierent
again.
[Updated: 4/12/2017]
1. The lathe out of the box and we are ready to start work. 2. Remove the chuck guard.
3. Remove the end cover. 4. Remove the rear splash guard..
5. Remove the tailstock.
PLEASE READ THIS FIRST
© Arc Euro Trade Ltd, England 2012
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12. Remove the tool post.
13. Remove the detent plunger & spring from the compound slide.
11. Remove the drive belt.
14. Remove the ball handle and spacer. 15. Tap the compound slide to remove the micrometer dial taking care not to lose the friction spring.
8. Remove the transfer gear bracket. 9. Remove the tumbler reverse lever assembly. 10. Remove the belt cover.
16. Remove the dial bracket. 17. Remove the compound slide & gib. 18. Remove the feed screw. 19. Remove the slide base.
20. Wind the cross slide o the feed screw. 21. Remove the cross slide & gib. 22. Remove the ball handle & washer.
© Arc Euro Trade Ltd, England 2012
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31. Remove the screws holding the rack. 32. Remove the rack from the front of the bed. 33. Remove the chuck from the spindle ange.
26. Remove left hand and right hand leadscrew carrier brackets. 27. Slide out leadscrew.
23. Remove the micrometer dial & friction spring. 24. Remove the dial bracket. 25. Remove the cross slide feed screw.
28. Undo the screws retaining the leadscrew cover... ... and slide out the cover.
29. Undo two screws to remove the apron from the saddle. 30. Slide the saddle o the end of the bed.
© Arc Euro Trade Ltd, England 2012
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34. Remove the power board cover. 35. Disconnect the mains leads.
36. Remove 4 screws retaining the control panel and lay it down beside the machine. 37. Disconnect the earth leads.
38. Disconnect power cables and guard
switch wires.
39. Remove the motor cover and pull power cables through from front of machine.
40. Remove motor end cover and mains cable 41. Remove the power board
Dismantling the spindle
Steps 34 to 77 include a bearing change from standard ball raced bearings to taper roller bearings. Switching to taper roller bearings will improve the machining
accuracies and nish.
Since in many cases, taper roller bearings are not an essential upgrade, and because you will need access to another lathe, a hydraulic press and
bearing separator you may wish to keep the standard ball races and skip forward to step 77.
© Arc Euro Trade Ltd, England 2012
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48. Press out the spindle assembly. 49. Press out the rear bearing. 50. Spindle assembly removed.
42. Remove the leadscrew guard. 43. Remove the 2 hex socket and 2 hex head screws securing the head to the lathe bed.
46. Remove lock nuts, gear, belt pulley,
2 spacers and the key from the
spindle rear.
45. Remove the front bearing
cover screws.
44. The head may now be lifted clear
of the bed.
47. Remove the rear bearing
cover.
51. Press or pull o bearing and remove bearing
cover from spindle. Note the bearing t.
If the bearings are tight to remove, polish the
spindle journals. The front bearing can be a press t on the shaft but the rear bearing needs
to be push t to allow accurate preload adjustments to be made by the two C-nuts.
52. Polish the spindle and test the t by using
one of the old bearings (if not damaged).
53. Fit bearing cover and press on
nose bearing.
54. Press front and rear outer bearing races into the head.
© Arc Euro Trade Ltd, England 2012
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55. Re-t the head and lock down. 56. Re-t the leadscrew cover.
57. Grease the front race and rollers and assemble. 58. Fit the front bearing cover. 59. Grease the rear race and rollers and t.
60. Fit the rear bearing cover. 61. Fit the key and plastic spacer. 62. Fit the spindle drive belt pulley.
63. Check alignment of drive pulleys and adjust
spacer behind spindle pulley if necessary.
64. Fit the outer spacer and gear.
65. Fit the spindle C nuts, adjust out bearing
backlash with minimum preload and only
nip up the C nuts for the time being.
© Arc Euro Trade Ltd, England 2012
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66. Fit the power board 67. Thread wires from bottom of motor board through motor cover and then through bed to front.
68. Fit motor cover. 69. Connect Mains In to top of board. 70. Fit power board cover.
71. Reconnect the earth wires to the head.
74. Check the gear alignment. 75. Adjust this spacer to correctly align the two gears.
72. Fit the power wires to the emergency stop switch (noting correct
orientation) and t the guard switch wires.
73. Temporarily t the belt cover and tumbler
reverse lever assembly.
© Arc Euro Trade Ltd, England 2012
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Running the spindle for the rst time:
1. Follow the Start-Up procedure with the motor running forwards.
2. Run the machine at a low RPM. The machine should run smoothly with minimal noise and
vibration. If not turn o the machine and investigate the cause of the problem.
3. Increase the speed and run for 10 minutes at a higher RPM.
80. Run the spindle following the procedure below and check the belt is centred on the pulley. If not
the motor angle may be adjusted by slackening these screws. Check the belt tension again.
76. Remove the tumbler reverse
assembly and belt cover again.
77. Fit the drive belt and adjust the belt tension. 78. Belt tension adjustment screws.
79. When adjusting belt tension, it should
twist easily through 90°
81. After running 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. Re-t the belt cover.
© Arc Euro Trade Ltd, England 2012
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88. Place the saddle on the bed and
check to see how it sits.
89. If it rocks, blue the bed and slide
the saddle up and down to nd the high
spots.
90. Scrape, le or stone down the high
spots until the saddle sits at on the bed.
91. Loosen shear plate adjusting screws below the level of the plate and loosely t to saddle. 92. Oil bed and saddle and slide saddle onto bed.
86. Drill and tap the xing holes deeper if necessary. 87. Final t rack making sure it seats properly in the corner.
Carry out all the following adjustments to both the
front and rear shear plates step by step.
93. Lightly pinch middle cap screw.
94. Screw in adjusting screws until just touching.
95. Slacken the middle cap screw.
96. Screw in both adjusting screws 1/2 turn.
97. Pinch up middle cap screw.
83. Scrape any paint o the bed shears.
85. If necessary, radius top rear edge of
the rack and trial t again.
84. Trial t the rack to check if it seats well or rocks.
98. Test slide saddle up and down the bed. There
should be slight drag with no free play. Lightly
pinch up remaining cap screws checking after
each one and adjusting as required.
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