Not sure this is the right place to post this, but it was certainly a mistake, just not mine.
When I bought my new SIEG C4B lathe it was a replacement for my little-used Unimat SL, so a huge step up in power and rigidity. A few practice pieces showed it to be more than adequate for anything I am likely to do with it, but when I used the power feed the result was very poor with the drive slipping intermittently.
After much head-scratching and dismantling I eventually discovered that, while the leadscrew had a left-hand thread, the half nut was right-handed! You can imagine they didn't engage very well
It took a fair bit of correspondence and some photographs to persuade the supplier (Axminster) that I knew what I was talking about, and a good deal more time waiting for the replacement parts to be shipped from China. To be fair, Axminster offered to replace the machine but by then I had completely stripped, cleaned and re-assembled it and mounted it on my home made stand so I opted to wait for the bits.
Once the correct parts were installed it was a whole different experience and my initial doubts about my purchase quickly disappeared as I cut a few practice threads with ease.
I doubt if this is a common fault, but something to think about if you have a similar problem.
