Reconditioning a Relmac lathe

[m_c]

Why not remachine the existing back plate?

Unless you need to remove a lot of metal to make it suitable for a new chuck, then it should be fine.

[irving2008]

Why not remachine the existing back plate?

Unless you need to remove a lot of metal to make it suitable for a new chuck, then it should be fine.

Because a modern chuck requires a larger boss. Currently it has a 4" chuck with a 3" recess but modern 100mm chucks have an 80mm recess. Also there is possibly a problem with the backplate itself, but until I can clamp it up on a known good machine to measure both axial and radial runout accurately I can't be sure...