End mill identification

[Lagonia]

I am fairly new to machining. I have a PM-949TV mill and a PM-1440GT lathe. I have done small projects, nothing extraordinary. My father in law, who was an old time machinist working for the Union Pacific Railroad, recently passed away and I ended up with a lot of his tooling. Part of this tooling is what appears to be a set of end mills with some sort of a guide attached on top of them - the guide can be removed and a different one attached on top of the end mill. The best I can tell is that these end mills are used to enlarge existing holes?

I am attaching a couple of pics for reference.

Thanks!

 

[devils4ever]

They almost look like router bits to me.

 

[Canus]

I have a few of the same. I use mine to create a counterbore to recess the heads of socket head cap screws.

 

[MrWhoopee]

Counterbores w/ interchangeable pilots.

 

[Lagonia]

Awesome, thank you guys!

 

[benmychree]

Yes, counterbores, they can be used for spotfacing too.