Drill bits

I was at the hardware store the other day, looking at the drill bits. Here’s what I found in the way of selection and price for a 1/4 inch drill bit. Now I have more questions than when I visited the hardware store. As you might expect, none of the staff there knew anything about drill bits, other than where they were located on the shelves. So I’m hoping the experts here can offer some info on drill bit selection.

These were all made by Dewalt as I recall.

  • Black oxide, $2.99, recommended for general purpose use.
  • Titanium coated, $3.49, recommended for wood or metal.
  • Cobalt, $5.49, recommended for heavy metal.

If you wanted a drill bit for drilling both wood and metal, and were willing to pay more if it stayed sharper longer and/or made tough metal drilling jobs easier, would it make sense to buy a Cobalt version? Or are cobalt drill bits no good for wood, only good for metal? Wouldn’t any coating on a drill, like titanium coating, quickly wear off the first time you drilled something? I don’t see how a coating would be much help. Is a cobalt drill coated with cobalt, or is the entire bit made a cobalt alloy? Are any of these bits actually just a hardened, tempered steel, like drill bits used to be made? Can all three versions be sharpened by the diy’er? Or are some of these types not possible to easily sharpen?

I don’t know the advantage of titanium coated drill bits over oxide bits other than price. The Cobalt drill bits I am familiar with were for drilling holes in Cobalt Chrome alloys. Short of a diamond coated bit, a cobalt bit is about the only thing that can drill through that alloy. You could use it for almost anything, but it is expensive and I don’t think you can sharpen it with home type equipment.

I’ve found that titanium nitride coated are no better then regular tool steel. Cobalt drills are vastly superior. They go through fairly hard steel like butter and are second only to carbide. They are also fine for wood. Well worth the difference in price.

I have to agree with MY 2 CENTS here because I use cobalt bits for everything. I’ve had most of them for years and there was never a need for sharpening them. I’ve never broken one either so they are worth the extra money in my opinion.

Good high speed alloy steel bits will get most jobs done in wood plastic or most un-heat treated metals as long as they are sharp. I swear by my Drill Doctor bit sharpener for that! For heat treated steel, carbide is the way to go. For high alloy, cobalt works good. I haven’t used cobalt very much but they can be ground sharp again with good stones.

I only buy cobalt bits. Nothing I’ve ever bought has come close to the performance of cobalt. They’re worth the extra money.
The titanium over black oxide is intended to act as a lubricant for the cutting edges.
Carbide is the hardest, and on all my other cutting edges I buy carbide. I use a lot of small bits, and carbide is too brittle for small bits.

Which brings up an additional point. Most people use way too high a speed when drilling metals. The cutting edge needs time to cut. I keep my drill press on its lowest bit speed, and it produces nice “curly fries”, which is exactly what you want to see. My hand drills are variable speed, and I always drill slowly in metal.

Should lube the bit also,Bowman used to sell some seriously good drill bits,dont know what they called them,but avoid frustration and spring for the better bits and when you find good reasonable priced bits,buy an extra set,they have a way of being hard to find when replacement time comes and Same is exactly right,you have to watch the speed of the drill bit,you can ruin them pretty quickly when they are not cutting.

+1 to Kevin’s suggestion. Lube the bit when drilling/cutting metal. Machine shops use systems that feed “machine oil” to cutting edges, but for the average homeowner a can of 3-in-1 will work wonders. And remember that drilling metal IS “cutting” metal. You want the bit’s edge to cut rather than wear its way through the metal.

One additional tip: when using sanding or grinding tools on aluminum, liberally rub chalk on the sanding/cutting wheel/disc/head/whatever before starting to keep it from “loading up”. Sidewalk chalk is worth keeping on hand. An old machinist taught me that trick years ago, and it really works.

Sometimes, you can get away with buying cheap tools when they aren’t used very often. Drill bits are one exception, unless you only work with wood and plastic… :wink: