I’ve a Baileigh Industrial TN76 H. It looks the business beefy as hell. Yet you can see it twisting in use.
I’ve lost count the holesaws I’ve broke teeth off.
I made a tube notcher shear tools may years ago but it wasn't for one offs You could cut over 1000 notches in 531 before needing to sharpen. They were for designated machines
I worked for a wheelchair manufacturer and made 200+ chairs a week there were a lot tube notching to be done. For odd size tubes end mills were used but if they weren't sharp the would buckle the tube ends.