I recently worked on a project that required drilling a 1/4" hole in about 1/4" thick hard steel. I went through 6 drills that were in my shop. Nothing special. Now they are in the shopping cart. I kind of crushed the steel. Then I got DeWalt zirconia drills with attachment. The start went well, that's all. At least I had more than one dent now, but still no holes. The project has stalled. I then ordered cobalt drill bits from Revain Bosch. I had 3 different sizes although I only needed 1/4" bits. WOW! Doesn't matter. I had to slow down on my drill press and oil the hole frequently. It didn't look like oil drilling but the holes have been coming up fine. Since then I've had to Drill 2 new and larger holes (3/8") in some softer 3/16" steel. I had to use an adjustable electric hand drill. Back to Dewalt 1/4" cobalt drill bits. . Drilling went well, but I found I needed a little more than the lowest functional drill speed, but not too high. I also used frequent lubrication. I used a Dewalt Zirconia drill bit to increase the initial 1/4" hole to the desired 3/8" hole. This also went well. I'm happy. If only I had had cobalt drills at the start of these projects. I am ordering more cobalt drill bits from Bosch in other sizes and plan to keep them separate from my other drill bits. It seems to me that all drills are the same.
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