What is this tool?

[RickVS]

Any idea what this tool does? Looks like a screwdriver but the business end just has a series of ridges.

 

[Ian]

It could be a re-threading tool (basically a tapping tool) - it'll create threads when using this on a slightly smaller diameter hole.

 

[Rparky1]

It looks like a screw starter, for use in wood. I have had one for many years.

 

[AC Power]

Agree with Rparky1.