As asked for by forum members, here is an update on how my my Sieg sc3-400 upgrade is fairing. My previous post has been moved or deleted so I will give a quick refresher.

The motor control board blew in the lathe after a jam. I repaired the control board with new chips, transistors, capacitors and diodes and the lathe worked as new for about three weeks and then switched on one morning and everything was dead. No fuses blowing this time, no tripping RCDs just totally dead beyond the filters so rather disheartened I figured the repaired board was not worth another attempt to bring back to life as I had somewhat butchered it on the initial repair.

So the choice was to buy a new control board £200ish (not a good idea as the original didn’t last a year) or upgrade. I bought a TEC motor and controller, and pinched a few bits from my stock of electrical parts.

VFD is a TECDrive IP20 0.75kW 230V 1ph to 3ph AC Inverter Drive, EMC

Motor is a TEC IE2 0.75kW Aluminium Three Phase Motor 230V/400V 2 Pole 71 Frame

Lathe has a speed controller in the same place as before and a forward/off/reverse switch on the front. At the moment the rest of the original fittings are there to keep out dust and debris. Power on/off is via the 10 amp MCB in the supply box.

It’s a beast of a set up but nice and quiet. Very impressed with TEC.

At the moment, because I need to make a few parts, the motor is fixed to a welded frame and fitted to the original motor mount on the lathe. This moves the drive spindle off centre due to the size of the motor but it is only a temporary set up.

The plan then is to extend the motor drive shaft a couple of inches and bring the spindle and thus belt closer to its original position. Hopefully this will enable me to refit the gears and selector as well as the protective cover (with a shaft hole in it). If not I shall ponder alternatives.

Will keep this post updated as things progress.

Mod edit: rotated photos

Edited By SillyOldDuffer on 15/03/2022 14:14:56

I had never owned a lathe before and couldn't see the point of spending a small fortune on one when initially it was only going to be used to make a few parts for a motorcycle. Trouble is they are so addictive once you start using them..

It's absolutely brilliant for me and i'm perfectly happy to do this sort of repair/upgrade. I have learnt lots and still so much more to learn. I now have a much better understanding of what i want from a lathe, what's good, bad, annoying and just plain stupid and when retirement looms i may upgrade.

I did forget to post a pic of the drive controller (see below). It's wired from a circuit on the house consumer unit which is 30mA RCD protected. The 10Amp MCB is what i use to switch on and off. There is a quick blow fuse wired next to it (don't think it will go before the MCB or RCD but was specified in the book for the drive). The control box is Earthed to the main earth terminal. The motor is fed through screened cable that is earthed on the VFD. The control cables are earthed only at the VFD control box as earth loops are to be avoided. I did not fit fans as i prefer to leave the door open and have the motor speed display.

It is working great. On to stage two..

Edited By JasonB on 16/03/2022 12:17:40

https://inverterdrive.com/

I have since found a drive on there that would supply the original dc brushless motor that the lathe came with (but where's the fun in making things easy!!)

It was the easiest option for me. 1 motor, 1 VFD, 1 10k pot and a three way switch.

British made motor and drive. 2 year warranty as they were bought together.

Can't fault it so far.