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

I used this to drill a hole in 1/4" thick 316 Stainless Steel. I used canola oil to lubricate. This drill bit cut quickly and cleanly after using a 1/8" bit to drill a pilot hole.

Did the job and very good quality.

Used this drill bit to drill 48 holes in 1/8 inch thick 1-1/4 inch x 1-1/4 in aluminum square tubing. Worked great!

Thick, strong, durable, and well made drill bits. Easy to use and quite versatile.

I haven't had a chance to really use these yet. I have a set of older bits I am trying to use up before breaking into these new bits. I have used it a couple times and I wasn't as impressed with the drill speed given other reviews and videos on them. I think they did just fine and better than most but not by a large or even meaningful difference. I haven't used it on a lot of material types, so it may be better suited for something I haven't tried yet.

Bits are sharp and keeps a good point. It’s hard to find drill bits that last.

Had a stripped and destroyed lug nut over a stud, tried other drill bits and they burnt out before i could get close. These drilled through the whole thing within a couple of passes and they actually last. If you’re drilling out hard metals these are awesome.

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.

great

Sharp, stayed sharp, cut through 10mm HDPE over 100 times like butter. Great tool bit.

De lo mejor que he probado en brocas de recubrimiento de cobalto. Sin considerar aceros de gran dureza, tiene un excelente desempeño de corte y velocidad, puedo suponer que por el ángulo de ataque de la broca. Mayormente la he usado en taladros de banco de 3/4 HP y aceros, hierros e inoxidables. Recomendado al 100%

Excellent

Excelentes brocas, sin problema alguno para perforar metales