Trying to revive this old vice looks like an early one. It won't tighten and just slips. I've tried in different locations but still slips. I think there may be something wrong where the half nit is located . Any thoughts?f
The second photo shows the half nut and Spring. The vice no. Is 674409 no.52 would be interesting to see the original Spring, set up. I'm pretty sure there's not enough tension in the spring and this is causing the thread to ride over. However, there is quite a big slot in the half nut for the bar could this cause the slipping, you can see this please follow n the photo too.Post a photo of your spring and release lever.