コバルトドリルビットセット M35 HSS ジョバー長さ 29個 (0.08インチ-0.5インチ)

They're mostly good drill bits , nice n sharp. But I give 3 stars because I had two of them snap fairly easily within the first few uses.

I work with metal daily, so I go through a lot of drillbits. cobalt is great for working with metal but it can be brittle if you don’t know what you’re doing. I read some complaints about people snapping their bits and I have yet to do so, and have been using them for months. For the most part, they stay sharp and cut well as long as you take care of them and use them at the proper speed and pressure. The size of the set provides the sized bits needed so that I can properly drill and tap a hole. The one major problem I have with this set is the rounded shaft. All bits are completely round and if your bit bites in the medal, the drill chuck will spin and strip on the shaft. This will happen often especially with the larger bits. That’s annoying in itself but when makes it really bad is the fact that the drillbit sizes are etched exactly in that area, so you essentially strip off the drillbit size label very easily, and the only way to make sure you have the correct size, is you must stay organized and keep it in its case and its proper spot. For this reason, I highly recommended purchasing the option with the metal case provided. Overall, it’s a great set and I’d likely buy it again based on its price point and quality.

Not very sharp, maybe 2-3 time use each.

I really enjoy the extra durability of cobalt. These sat for a couple of weeks but when I did use one, it cut right into what I was working on.

I had to drill 4 holes in some forged steel. The final size I needed was 1/2. I used lots of oil and went from 1/16 and slowly stepping up to 1/2 by incrementally using each size. It was tedious but seemed to work. They lasted for two holes, I broke 3 bits, went incredibly slow RPM and used a lot of cooling oil. Initially they seemed to drill just fine but Some bits didn’t even last a minute or so before their cutting ability failed. They were totally inadequate for the project at hand.