My experience of the cheap USB ones has been poor. As Brian says getting enough light to see anything useful is difficult. In addition, the ones I used had fairly long focal lengths* and narrow fields of view, so anything close is difficult if not impossible to see with precision. It is also difficult to control the direction the camera is looking when it's on the end of a flexible USB cable.
I hope you only want it for inspection. Using one with the lathe running is likely to be an accident in progress.
Have you considered a dental mirror type device.
* Just looked at a couple of the better £40(?) ones online and they quote best viewing distances of 5-10cm.
Edited By Peter Cook 6 on 26/09/2022 18:43:25
Edited By Peter Cook 6 on 26/09/2022 18:50:58