"Bought the pack of five with a specific job in mind. I wanted to drill a 1mm hole across a piece of 3mm Steel tubing used as a shaft for a Model Helicopter.
The shaft was already centre drilled with a smaller black HSS drill i had.
The first 1mm drill from Screwfix snapped as i increased the pressure because the drill was clearly not cutting.
The second 1mm drill also failed to start cutting, so after that i gave up.
When looking at the remaining 3 drills in the packet they all looked a bit different ..... different amounts of coating and flute pitches. Width measurements with a micrometer showed reasonable accuracy.
I can only recommend these for use on materials such as wood, plastic and most non-ferrous metals."