If you can cut through the threads of a spare bolt perpendicularly with a junior hacksaw on either side, but not all the way through. That will make do as a homemade tap which should assist.
Why does a tap need those cut-outs?
@Tijmen started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
If you can cut through the threads of a spare bolt perpendicularly with a junior hacksaw on either side, but not all the way through. That will make do as a homemade tap which should assist.