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

Did the job and very good quality.

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

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 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.

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.

5/27/2026 : great drill bits. Nice storage. Awful labeling. I had to use tape and marker to label these for myself. Bosch really needs to fix this. Already some numbers were hard to read after a little dust got on the case. Even the labels on the bits are nearly impossible to read. Why Bosch? Who are those labels meant for? People who WANT to make silly errors, and make life so much harder than it needs to be. Take my advice. Label it carefully yourself in five minutes, and save yourself HOURS of cumulative time trying to figure out which size is which.

Worked well for what I need you to do. Bites well

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

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%

Excelentes brocas, sin problema alguno para perforar metales

The 5/64, 7/64 and 9/64 inch sizes are basic smaller drill bits. They are ones you are most likely to break in a bit set. So you will likely have to go shopping for replacements for broken bits in these sizes. I recommend the reasonably priced Dewalt DWA1205 and DWA1207 for the first two sizes and the Bosch CO2136 for the 9/64 inch. All are available from Amazon.