I've been experimenting a "DIY" abrasive tube notcher to cut some seat stays/seat tube connections since I could not cut them by hand. Rudimentary aspect but happy with the final result! :
Abrasive Belt Tube Notcher | Pipe & Tube Machines Ltd
Abrasive tube notcher « Blog: oTm Bikes
Abrasive Belt Tube Notching Machines | EC Hopkins Limited