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Friday, December 17, 2010

Cleaning of SIEG C4 lathe

As the lathe was covered heavily with protective red grease, my first task was to clean it all off and lubricate the machine properly. As I was cleaning the lathe, I notice that the bed number was 00425, meaning that this is a very new model and I got one of the "first ones". Just for comparison, the previous SIEG C2 lathe I had was with a number of 22xxx.

For cleaning I used paper towels and lots of turpentine that I spread with a small paint brush after getting most of the smears of grease away with the towel and finished with a turpentine soaked towel. The bed way was quite easy as well as the slides and took me about 30-45 minutes.

As I removed the chuck to clean the spindle end, I rotated the spindle to get to the bolts and heard small grinding sounds. Thought first that the spindle bearings are already broken, but when I disengaged the spindle from the auxiliary axel the sound stopped. This required a peek in to the headstock, so I unscrewed the cover on the casting and noticed grease on the gears.

Nope, it was not grease. Metal gears covered in thick greasy like substance that felt more like a coarse lapping compound. I don't know if they have lapped the gears in place for quieter operation and in a rush didn't bother to clean it up or is their grease gun full of small grinding particles and chips.

As I didn't want to disassemble the headstock at this time, I tried soaking the gears in engine oil and rotating them. The oil was mainly picking up individual partcles, so I tried with turpentine and found out that it flushed the grease quite nicely, but didn't get everything. I ended up using both, first soaking with turpentine and then with oil and couple of times wiping with a paper towel between the teeth of the top most gear. About five minutes later I had a nicely working and soundless headstock gear pair.

All the accessories went through the same turpentine treatment. The change gears had thick red grease on them, mixed with dust or something similar. The paint brush and a pail of turpentine got rid of everything easily. A nice feature of these all metal gears is that the hole in the center is a free siliding fit to the respective axel as opposed to the C2 lathes plastic gears, that had a hard friction fit which was a PITA.

I removed the lead screw cover to examine the lead screw closer. The lead screw was covered with the red grease and a closer look revealed that there is only grease on it, so for now I left it alone. However, I was intrigued to take a peek of the pillow blocks that hold the screw to see if there is anything better than the C2 lathes cast iron blocks. The tailstock end seemed to have a bronze or brass bushing where the screw rotates and the block itself was pinned and bolted. These hardened pins are an indication for me of precision, as they lock the block in certain place and position.

In the headstock end of the leadscrew I had to remove the plastic electrical box to see the screw. The electric wires were protected from the screw with a small floded steel sheet and under that was a very positive surprise: A flexible connector and a thrust bearing! Seems that SIEG really has thought about these things and this really is showing up as a quality product so far.

The carriage also had some interesting features. In the photograph to the right I circled some items from the top view. Yellow ones are threaded holes that have a grub screw to protect it from swarf and these are for some sort of attachments/accessories. The blue ones are for adjusting the front side gibs that hold the carriage down. The green ones are yet again hardened pins to align the apron to the lead screw. The red one is for locking down the carriage to the ways when for example parting off or taking a truing cut with the cross feed.

I removed the carriage front side gibs or "paws" to clean them up. They had the same red grease all over and some paint chips on them. I'm just a little bit confused as to how I should adjust these, as the lathe manual is of no help at all and these are different than in the C2. There is no obvious adjustment screws that would counteract each others, there is only those two small socket head cap screws that hold it in place. I just snugged them up a little bit so the carriage won't lift, but in the end the cutting forces are pushing the carriage down to the prism way, so I think these paws are just to keep it from lifting up easily. If someone knows better, write about it in a comment to this article.

Behind the right hand side paw there is a locking element that locks the carriage to the ways. I did not have a magnet at hand so I didn't remove it, but once I find one, I'll check it also. I'm suspecting that it is just a little bit of L-shaped and the only screw just lifts it up to lock the carriage from movement.

To get best access to the electronics compartment located in the back of the lathe, I had to get the gear cover off. This means removing every gear and the drive belt. While removing parts I cleaned them all and noticed a nice desing feature on the gear axles: They have an oiling port in the visible end and a small hole goes halfway through the axle and then there is a cross drilling. This provides oil to between the axle and gears to lubricate them properly. Very clever idea!

The gear covers frame however had one error: It will not come off if you don't first remove the four small screws on the backside of the electrical box that is located inside this gear compartment. I think I'll just take a Dremel or a round file and make some sort of small cutout to the frame where the screws are located so it slides in and out without unscrewing those small screws. Otherwise the end shows the usual SIEG style of finishing with a paint on parts half assembled, as indicated by the paint spots.

The controller board, as seen in the above photos, is located in the large box behind the lathe. There is a hefty finned heat sink that provides cooling together with a small fan to full wave bridge rectifier and six huge (probably) MOSFETs. The capacitors are so big that there is a cutout in the heat sink for them. The board itself has nothing special except very good connectors. There is a small additional daughterboard connected with a couple of rows of pins and this contains an ATMEL microprocessor. Didn't look that closely but I suspect that it is responsible for operating the display and keypad.

As I put everything back, I ran into a problem: How to get those small wires through the white plastic tube that goes through the headstock and is already full of wires? Well, found a length of copper wire, pushed it through and made a small loop and to this loop I attached the wires and pulled them through.


  1. Jaako,
    could you please report the out-of-the-box accuracy/runout on this machine? I am in the process of a possible upgrade of my own lathe, and this seems a good candidate. Overall, does it seem like the same quality as your previous Sieg, or something better?


  2. Hi Ed and thanks for asking that question. I'm just writing a "pros & cons" aricle of the lathe, so be sure to check it out in a couple of days ;)

    One thing I just figured out is that the usual SIEG measurement report paper was either missing or not included at all. But no problems, I had a dial test indicator in my measuring tools so I used that to check spindle accuracy only.

    I chucked up a 10 mm hardened and ground pin in the 3-jaw chuck and measured 50 mm from the jaws. I took three measurements, each with different keyhole used to tighten the jaws. One jaw clearly indicated the best condition, total indicated runout (TIR) was only 0.03 mm. Very good for a cheap 3-jaw chuck.

    The spindle MT3 bore showed TIR of 0.005 mm or less, so the spindle has good bearings and a bore that runs true to them. Basically this kind of measurement means zero, as the measured value is not accurate.

    The spindle index for the chuck showed the same, TIR of 0.005 mm or less.

    The spindle face showed a TIR of 0.01 mm or under.

    The surfaces were a little bit oily, as I only wiped them with paper towel and my fingers.

    Overall the build quality is definately there and muc better than the previous C2 lathe, in more ways than I can count :)

    If I'm asked, this is a good machine for a hobbyist or a small scale user.