Sieg lathe modification questions

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Nikhil Bhale

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Location
Vidharba, India
Hi,

I have a Sieg C4B lathe. I am in process of renewing the spindle bearings.
The lathe has one tapered roller bearing 32007 at front and a deep grove ball bearing 6206 at rear end.
As the rear bearing pocket is deep enough I am planning to fit a axial thrust bearing 30206 there. Some machining of the bearing spacer will be required to fit the bearing.
I have a question to ask about my next move. I saw on YouTube someone who has modified the headstock to have oil bath lubrication for spindle bearings. The mod is simple and requires plugging of headstock bottom to hold oil and putting of oil seals at both ends.
Is there any advantage of oil bath lubrication over grease lubrication for a small lathe? I have ordered both the front and rear oil seals for this mod.

The other major mod is that I got lucky and came in possession of new old Delta M VFD of 1.5kW single phase to three phase for about $70. I am now looking for a suitable motor to run this VFD. After searching for a long time for a 220v 3 phase motor in India I came to know that these motors are not available here. Either you get a 220v single phase or a 440v 3 phase motor only. So I am planning to get a 440v star connected motor and convert it to 220v by running in delta. Any idea if this will work in real?


Regards
Nikhil
 
Hi Nikhil .
About voltage of the motor - Voltage for each coil
380v / square root of 3 = 220 v
440v / square root of 3 = 254 v
You can use it with 220v/3 phase, but the motor will lose part of its power
About lubrication: grease lubrication is too good for needs, including for industrial machines. I won't change because it's a waste of time, effort and money.
 
Last edited:
Hi,
Finally I was able to renew the spindle bearings for my C4 lathe. I used tapered roller bearing on both ends. 32007 and 30206. I also modified the headstock to have oil bath lubrication. Oil level is kept so that it comes to middle of lowest roller. I read about this somewhere on SKF site. I am using Bosch GO90 gear oil for lubrication.
The roller bearing were preloaded so that there is no axial movement. Runout on the shaft is also minimal about a micron or 2. The shaft turns about half a turn if flicked by hand.
But I am facing some issues with this setup. The shaft is getting a little hot when the lathe is running. It gets to about 50-60C after 30 mins.
I am not able to pinpoint the exact cause for this. I don't know if its due to bearings or its due to addition of oil seals at both ends.

Regards
Nikhil
 
Nikhil .
The shaft gets hot about 60 degrees in 30 minutes, your bearing will be hotter than that temperature
Loosen the bolt by a few degrees, check the shaft run-out. If the shaft runout is more than you can accept then you only have 1 option (the most economical): as you have set up,
If you loosen the bolt a few degrees and the shaft runout is fine, loosen it a few more degrees....
 
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