Drill bits for steel, 3/8" and smaller

[brianwelch]

Spent some time over the weekend fabricating a steel bracket from a piece of way-too-thick-but-free steel angle. I needed to drill a series of holes ranging from 5/16" up to 1/2" in a piece of 1/2" thick steel angle...I used a series of drill bits to get the final diameter, and ended up breaking a few, (mostly under 3/16" or smaller) from a collection I have assembled over the years. There was zero tolerance in the hole layout, and for once, everything fit on the first shot...
What does the brain trust here suggest for best bang for the buck bits? Are the cobalt bits, quite more costly than titanium coated bits, (which seem pretty cost effective) worth springing for? The vast majority of my drilling is by hand, and in wood. (I always use a lower speed drill and a lubricant when drilling steel or cast iron, if that helps any...)
Thanks in advance

[AHill]

There's a guy on YouTube that does a pretty good job of testing tools. His channel is called Project Farm. He will tell you which tool is best and also which was is most affordable that can do the job. Here's a link to his test of drill bits for metal. I don't think it's a good idea to use drill bits designed for wood on metal. Drill bits designed for metal can do the job on wood, but generally don't leave as clean a hole.

Cobalt drill bits are much better than the titanium nitride coated bits. Tungsten carbide bits are also good, but they are expensive as well.

https://www.youtube.com/watch?v=xgQeSrsAXgE

Here's a tutorial posted on Grainger's website about drill bits.

https://www.youtube.com/watch?v=xgQeSrsAXgE

[brianwelch]

Great links...I have watched videos by the referenced YTuber, didn't think to check for drill reviews/tests...There is another that I was thinking of, but have to go back and check...
Funny, other than the obvious wood bits such as spade/Forstner/auger, never thought twice about using "twist" bits for drilling any material...
Appreciate the help!

[barryvabeach]

Brian,  I have a set of cobalt that I only use for metal sharpened to 135, they seem to last much longer.  No matter how big the hole,  I normally start with a small bit, then enlarge the hole by using a drill bit a few sizes larger, and so on.  I don't know if it is any better than just plugging away with the correct size to begin with, but that is the way I do it.

[KyleD]

Good working and lasting drill bits are one area where I feel you get what you pay for. Do not get hung up on the cobalt or coatings they are made of just make sure they are high speed steel and from a reputable manufacturer. The tempering process is where many of the imported mass produced drill bits fall short. An improper temper on the bit will make it too soft to hold an edge (rare) or brittle and prone to breaking (common) or warp the bit making it wobble. I have a set of Norse that are 20 years old. They have been sharpened many times and still cut great. I have broken a couple ver the years. all my fault. I have replaced several that got lost or were sharpened down to where they got to short.

[adamcherubini]

You want m42 US made drill bits. Chinese cannot source m42 and use a cobalt alloy that is inferior to M42. Expect to pay $100 for a small set.

The Bosch set in the video is made in China.

[barryvabeach]

You want m42 US made drill bits. Chinese cannot source m42 and use a cobalt alloy that is inferior to M42. Expect to pay $100 for a small set.

The Bosch set in the video is made in China.

Adam,  sorry,  I am a bit confused.  The Bosch bits say M42.  Are you saying they are not M42, or that they are a Chinese version of M42 which is not as good as the US version of M42?

[adamcherubini]

Adam,  sorry,  I am a bit confused.  The Bosch bits say M42.  Are you saying they are not M42, or that they are a Chinese version of M42 which is not as good as the US version of M42?

Yeah, I'm not sure why they think that's okay. Yes to both. M-42 is not a recipe. Its not a generic term. Its more akin to a brand name like Mercedes. Or maybe better, a specific model within a brand, like Mercedes S500. That S500 can only be produced in a Mercedes plant. M-42 is a designation within the ASTM A 600 spec (American Society for Testing and Materials). That spec contains inspection criteria and methodologies etc etc, all referencing other US specs.

What I think is, someone at Bosch thinks if a steel contains 8% cobalt, and 8% falls within the range in the ASTM spec, then the steel in question is M-42. By that logic, if you build a car that is comfortable and luxurious and fast, it is therefore a Mercedes Benz S500. It seems ludicrous but I think its actually pretty common. I bought "Hem Fir" at the home center the other day. What the heck is that?

The same is true for a host of other materials. AISI 1095 (American Iron and Steel Institute) is also a US spec material. Britain, Germany, Japan all have their own specs for steel (and everything else).

If you want really killer drill bits, buy US made M-42 bits from a US manufacturer like Triumph. And at this point, I think I'd have to say don't buy them from Amazon because they could be counterfeits like so much other stuff on Amazon. Choose MSC, Grainger, or McMaster etc.

[barryvabeach]

Adam, thanks for the clarification.

[Bob Vaughan]

Consider learning how to sharpen a twist drill.  Even if its made of the best gee-whiz steel, a dull bit isn't your friend. Sharpening isn't all that hard.  There are some people that will discard a dull pencil rather than figure out how to sharpen it.