Which tool to use?

[WesPete66]

So I was repairing a part and needed to make a flat bottom bore with a thread relief so I could cut an internal thread. (quickie sketch attached) I looked through the limited odd assortment of holders and boring bars that I do have and nothing was a good fit for the feature. I did get a good part made, but not a pretty one..
So, using HSS tooling on an Atlas 10E with quick change tool post, what would a proper tool be to cut an internal thread relief, and to face off the flat bottom of the bore? What would it look like?
Thanks!

 

[mikey]

I suggest you just go and buy one of these. With care, it will last the rest of your life. I have these in several sizes and they are quite good. You can also buy inserted carbide but they are finicky; if you get the speed and/or feed wrong you'll break off the insert in an instant.

 

[Parlo]

A common solution is to use the same tool as you will for the screwcutting, you know exactly how deep the bottom of the hole is. The shape does not really matter, I go a bit deeper than the thread and about 1.5 pitches wide.

 

[mmcmdl]

Sharp edge on the bottom bore with a 45 degree angle on the outer side . Usually 1 1/2 times the thread pitch wide . You can then thread out from the chuck without any worries . Mike's tool is the correct grind , whether you want to buy it or make it .