SlackBuildsOrg/system/recoverdm

This program will help you recover disks with bad sectors. You can recover
files as well complete devices.

In case if finds sectors which simply cannot be recoverd, it writes an empty
sector to the outputfile and continues. If you're recovering a CD or a DVD and
the program cannot read the sector in "normal mode", then the program will try
to read the sector in "RAW mode" (without error-checking etc.).

This toolkit also has a utility called 'mergebad': mergebad merges multiple
images into one. This can be usefull when you have, for example, multiple CD's
with the same data which are all damaged. In such case, you can then first use
recoverdm to retrieve the data from the damaged CD's into image-files and then
combine them into one image with mergebad.