I need to single-point an M8x1.25 thread on a 9.5mm tube with a 6mm bore. If I use an M8 die the remaining wall thickness will be too thin. I reckon I can do it with a standard 60 degree metric threading tool with a flat ground on the tip. By my calculations the flat needs to be 0.7mm wide. They make gauges for grinding the flat on ACME threading tools, but no such thing exists for what I want to do.

Any suggestions for how to grind the flat reasonably close to 0.7mm wide?

The matching female part will be bored to 7mm then threaded with an M8 tap. This is a non-critical part and will only be finger tight.
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