Depending where you got the mower blade(s), they're probably a dead soft 1040, 1080, some sort of hardenable carbon steel. But you also might find some dead soft carbon steel with an artifically hardened cutting edge, or you might even find some good alloy steels, depending on the source, application, and price point of the blades. There are some things you can deduce, but I wouldn't necessarily call those a "known material". They're better considered another variable.
The drill bits you get at Harbor Freight are another variable. I've got two of the big (115? 118?) piece sets. I've got the cheap (50 ish dollar) one at work, and the "better", (100 ish dollar) set at home. Some folks here have been happy with them. I'm not sure what they're doing with them, but they claim to be happy with them. I can't disagree with their conclusion, but it doesn't match mine. I fell into that rabbit hole. "I'll get the cheap set, just because it's the cheapest way there is to get an index"..... The drills are not straight, (Well, most drills are not truly straight, but these are down right visibly not straight). The drills are Not the size indicated on the stampings, and I don't believe it's an accident. The drills "might" be on size, but a couple to the left and right might be the same size, even though they're stamped for the hole that they're in... OK.... I only got them for the index.... Well, the reason I say it's not an accident... The holes in the index are sized for the drills they send. On size drill bits don't fit in every hole.... With all that said though, I have found some value in the cheap set. I took that one to work. Those drills never drill holes. They drill rocks and dirt out of disused bolt holes, they drill carbon buildup out of PCV ports, they get emery cloth taped on to them to polish pin bores that have gotten rusty. Things you really might not feel good about doing to a good drill bit that actually costs real money. That set has paid for it's self and half of the other set for that reason alone.
And I almost forgot the hardening... However they harden these drills (and probably how they get some but not alll of the same set SO crooked...), the hardening is just rediculous. Some of these things explode for no particular reason. Not every drill in the set, but a good number of them. They're just glass hard, all the way to the top.
Then there's the drill doctor. I use one of those at work, as we don't keep the "community bench grinder" in a good condition for sharpening tools of this nature. So the drill bit sets I have from Harbor Freight--- The flutes are not consistant enough to line up properly. Some sizes work dead nutz on the first shot. Others have the helix done non-standard, so the drills don't line up. Usually you have to manually clock those to get them to work out correctly. Not a "fault" of the drills, helix angles are not written in stone, and not all "good" drill bits choose to use a standard angle either. HF is the only set I've ever seen where they changed that randomly from one bit to another within the same set.
And then the drill bits you get at the box stores... Well, the grind is not guaranteed to be consistent from one purchase to the next, that's fixable. Again with the helix angles. Lots are fine, but no guarantees that you're not manually clocking the drill doctor. The quality (even if you have to fix the original grind) will allow for a pretty good overall experience right out of the gate, but all the brands, the house brands, the power tool brands, all the brands, your sharpenings are limited. My guess again is how the heat treating gets done. At some point they just won't hold an edge long enough to make a hole. In the mean time, they do work pretty well for bargain price drills, and have an arguably good cost/value comparison, but they're not an heirloom piece.
So the bottom line to all of that rambling... Box store drills are almost always light years ahead of Harbor Freight, and both can be a good value IF they're doing what you need, but neither are adequate for a "baseline" of what a drill bit should be. Don't let that confuse your decision any more than you should let a Youtube video set your baseline. Try some different drill bits. I know you said you're ready to purchase, but that's a big comitment. Find a place that's selling "good stuff", and get a couple of your favorite sizes. McMaster comes to mind for an easy place to do that. They don't have the best of anything (usually... But sometimes they do). But EVERYTHING they sell is pretty good. Their business model doesn't allow you to recieve junk, they're not equipped to deal with that. The brand you get might vary for a drill bit of the exact same description, but whatever brand it is, it'll be good. And the big internet stores... Just because two brands both have 5 percent or 8 percent cobalt... Doesn't mean that they do, and it doesn't mean they're interchangable. Put a couple of brands in a couple of common sizes in your collection and play with them. That will be YOUR answer. You'll never find an agreement between this forum, other forums, the internet at large, and your actual use. What works for YOU will be the best tool. What works for somebody else.... Well, great. That's what they should have. It doesn't mean that you're gonna be happy with it.
Don't loose any sleep over that. Forget Youtube. If you're doing only mild steel and harder, yes, the 135 degree tip would be preferable. By how much? Well, that depends mostly on whatever message the content creator would like to convey to you. Yes, 135 degrees is preferable for metalworking, but it's not night and day until you get into production. And although it'll still "work", 135 degrees is a very poor choice for a universal angle, for a drill bit that might be used on just about anything and everything that ever needs drilling. 118 is a much more universal angle.
Coatings? These can be magic. Like a suit of armor for your drill bit when it goes off to battle. They're also expensive. You can waste a small fortune burning up drill bits for general use. In my opinion, your "set" sould be plain or black oxide high speed steel. If you're doing something that's tough, by all means the plain drill bits will do it, but just become high maintennace. Enough to get you by until you can order a GOOD drill bit in that size. But that's personal choice/budgetary/preference stuff, that's not a functional decision. If you want every drill bit you own to be all suited up in armer and ready to go to battle with the toughest material you've ever heard of... Well, that's how it should be. If you want all of your drill bits to be.
Cobalt drills? Ok, so in the beginning, there was tool steel. (Which I suspect s a better description of the Harbor Freight stuff). Then we figured out how to alloy that in oh so many ways, made it better, and we ended up with high speed steels. Cobalt drills are just high speed steel drills. The difference is thet they are a much tougher "branch" of the high speed steel category. Kind of expensive, and tend not to be purchased where "normal" drills will work just fine. This is why you tend to see a much higher proportion of them soldd with a 135 degree tip angle. Because their projected consumers are "probably" not buying these drills to build balsa wood models...
Decent is only what decent is to you. This is why I suggest buying some singles. And test them. If you take a new, good drill bit, and ask it to do what you want it to do... Does it work? Does it work well? Document that. Is it not what you wanted? Document that. Then you'll know what you really want. The biggest reason that there are SO many options is simply that there are very few home shops, job shops, production shops, mass production factories, repair operations, etc who have exactly the same use case. Everyone wants something different from their drill bits. What YOU do with the drills, that's the answer. What works well, even spectacularly for others- In your shop that might be just another turd floating around in the bowl. And what works great for you, that might not be what works for 99 percent of folks with similar interests.
Great tools rarely come in sets. My advice again is to get a "decent" but not top end set of plain(ish) high speed steel drill bits for "reasonable" money, in a big, well organized way (like a 115 ish piece index...), and keep the specialized coatings, specialized tip grinds, special materials, etc, keep those as "for the job" tools.
So where am I at with drill bits? Well, I've got a (29?) piece set from Irwin. (whatever size is 1/16 to half inch by 64ths...), and they're good. I got the ones with the black and gold two tone spiral. It's not functional, the functional part is is black oxide drills. But I like that look. It's just marketing, but I like it. They won that game. They came from the internet, but they're box store/hardware store grade. Not great, but good. 118 degree and split points from 1/4. They'er awsome "universal" drills, and outside of metalworking that's WAY more selection than I need. So when I break enough of the regrettable Harbor Freight purchase (the cheap one was a fair gamble, the expensive one was a regrettable decision....), I've got a set on my saved list that I'll link to. They'll (mostly) only see metal, the quality is excellent, near as I can tell the grinds are good and consistant (but if not I can fix that easy enough), and I've just been very pleased with that line of drills. They're very versatile in what they'll do, but that doesn't mean they're the one for every job.... But I've used them, and they work for me. Because my "universal" drills are already very well covered for my use, I will have the 135 degree angle which goes much better towards metal work. The only thing I havent nailed down for 100 percent sure yet, is I believe there's a comperable set in metric, and I almost think I might want the metric version... Dunno. I won't be buying both. And I fully, 100 percent expect that I will still lean on my small collection of turbo nuclear specialized drill bits, as well as both reactively and proactively adding more specialized "loose drill bits" to my collection, because I know as well as anyone that there is no single drill bit that will do everything, both functionally AND cost effectively. And for what it's worth- Depending on the time and day, and whether Jupiter is in Taurus or Gemeni, Amazon might or might not be the best place to buy these-
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