uxcell 7pcs Spiral Point Tap Set M2 M2.5 M3 M3.5 M4 M5 M6 Metric Thread Screw Taps, Titanium Coated High Speed Steel 6542 Machine Tapping Threading Repair Tool

I used these while building a 3D printer. I tapped lots of aluminum parts and these taps worked great. I imagine they would work fine for mild steel as well. Probably nothing harder. For what I needed they were the right tool.

Works perfect for extruded aluminum and light sheet steel. Have not attempted other materials.

I needed a set of small metric taps to clean up female threads on used bicycle parts. These appear to be well made. I cleaned up a used stem that cost me $15 and would have been $80 new. The only issue was that one of the screw holes was lightly cross-started and all of them were dirty and full of old threadlocker. Ran the tap in from the good end of the threads, cutting out the cross-starting. With all the holes cleaned up, new screws go in effortlessly. Effortless is good when you've got to hold the stem, a handlebar, a screw, a front plate, and an Allen wrench all at once.

Worked well for adding a pocket clip to my knife scales.

Cheap readily available and a thread holes.

The taps worked well for me but just needed to clean up an existing thread.

These both are sharp like a knife, literally, cut through stainless steel like aluminum.

I needed to add some tiny 2.5 mm threads to a piece of plate steel. I was super worried these were going to snap in this giant piece of metal, but I went super slow and used a lot of lubricant and I was able to thread all 4 tiny holes with no problems. That tiny 2.5mm tap still looks practically brand new too. Completely blew my expectations out of the water. I used a hand turning tap handle and went just a couple turns, backed it all out, and then flushed the tiny hole with lube, then back again. Took maybe 30 min to do all 4 holes, but now they are threaded and work perfectly with my tiny 2.5mm screws. Recommended.