Bridgeport Slotting Head Tooling.

[steamy1]

I used to do lots of slotting with a similar Beaver slotting head mainly Keyway cutting.
On bores more than 5/8" I used a holder crossdrilled to suit a round piece of HSS of a larger diameter than the keyway to be cut.

On bores less than 5/8" the holder needs to be drilled axially or at a slight angle to give back clearance.

The HSS toolbit needs to be held in place by a grub screw in both cases.