BOSCH CO21 21-Piece Assorted Set with Included Case Cobalt Metal Drill Bit with Three-Flat Shank for Drilling Applications in Stainless Steel, Cast Iron, Titanium, Light-Gauge Metal, Aluminum

Great for hard metals, excellent product.

Excellent quality. As advertised.

Exactly what I needed. Got the job done and no issues yet.

Cuts all steel very well.

First use, very sharp and bored the hole quickly.But the curious thing is they don't have any indications of the drill sizes on the case, so you are left with using calipers, a drill guide, or taking a guess what the diameter is of the individual bits. Even cheaply made sets indicate what the size in the position is at the positions, but not this Bosch kit.

This is an excellent quality drill bit, and exactly as described. It's very long lasting, tough, and durable!

Worked great on my metal shed doors.

I've only tested it a few times on some thick steel angle iron, and once on stainless, but it showed no sign of dulling. It drilled through it like butter, after my cheap harbor freight drill bit just sat on the surface making a hot divot instead of a hole. I used cutting fluid (WD-40 or water works if you don't have your tapping fluid around), and I always recommend cutting fluid as well as stopping to cool before there's any smoke or smell of hot metal/fluids. Getting a drill bit too hot is the best way to ruin it, besides using it as a pry tool.I drilled right through a stainless steel hose clamp, which my cheap titanium coated bits won't even make a dent in.The price is great, and the bit definitely cuts into hardened steel like a champ. I'll be using these for drilling easy out holes and whatever else I need.I haven't checked the dimensional accuracy, but it has no visible bend or wobble. I will say it walks around instead of starting where I want it to, unless I use a center punch. That is not a problem for me, because I normally do use a spring loaded center punch, but I have noticed some bits walk more than others. I would say this one walks a bit more than the cheap, soft ones, but once it starts biting it goes right through your steel.I'll be ordering some of these in the common sizes I drill for tapping holes (for me, that's 5/16", 1/4", 3/8", 4mm, 6mm, 8mm). I'm not sure this brand offers metric sizes, but I'm going to look.Disclaimer: I'm not a machinist, and no expert on drilling. I'm just a hobbyist that does a lot of customized repairs around the house, RV, Jeep, and motorcycle.