Blind Hole Keyway

[Tel]

How I would get rid of most of the metal first is to turn a plug to fit the hole with a head on it, then mark out the keyway position on the head, place the plug in the hole and drill a hole through it, which basically gives you nearly a whole keyway that you only have to clean up.
I use this method quite often for a blind keyway I have to do, I also drill a hole in through the side of the shaft for the keyway to end in.
Will

And that gets my vote as well - it's how I usually start internal keyways and saves a lot of work. It often pays to make the plug pretty firm, and drill and tap the centre of it for a pulling screw as well.

[platypus2020]

I have a National Machine keyway miller, bought by my FIL in about 1967, that I have used to cut keyways in a blind hole. They don't allow you to run the keyway all the way to the bottom of the hole, it it comes close.