molybdenum or cobalt drill bits

I've had it with the cheap Dewalt bits i've been buying. It's time to invest in some good bits for drilling metal. Now i've used cobalt bits before, but i've never used hi molybdenum bits before. Which are going to be best for steel?

I am looking to buy something like a 29pc set up to 1/2". I usually don't need larger than 1/2" or smaller than 1/8".

Every time someone here on GJ asks about quality drill bits Norseman is mentioned so here is a link to Norseman:
http://www.norsemandrill.com/Catalog_Index.html

^^^^

Thanks, but that's not what i'm asking. I'm asking which is better cobalt or molybdenum.

I buy the cobalt on sale from ENCO and they are very durable for drilling into very hard steel.

Hope that helps you out.

There is no "better", but as a machinist of 15 years, I can tell you that standard high quality HSS bits are good for 99% of the drilling tasks that anyone would do.

Professional shops generally only use cobalt, moly, or solid carbide when doing long runs of stainless or similar, or drilling very hard alloys or hardened steel.

The vast majority of jobs use plain old 118 point HSS bits.

I recommend 118 HSS bits from McMaster, you'll get a US made bit such as Chicago Latrobe, and it won't break the bank.

You'll be amazed at just how insanely durable a very high quality HSS bit can be.

If you want to invest in Cobalt or Moly, there's absolutely nothing wrong with that... they will last longer when drilling metals from steel on up. If drilling aluminum or anything less hard than steel, plain HSS actually is superior because it takes an extremely sharp edge and is easy to hand resharpen.

IMO the best solution for a home shop is to buy 118 HSS or Cobalt bits (or moly if you prefer), and use a spotting drill (some people use center drills, but they're actually meant only for drilling center points to be used with live centers on lathes, spotting drills are meant specifically for starting drills), also, but a nice Centerpunch such as a 18B Starret will be a godsend if you're trying to do good work.

Cobalt is great, keeps my drills working longer, but so does cutting oil.

filtered said:

Thanks, but that's not what i'm asking. I'm asking which is better cobalt or molybdenum.

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Neither. High Speed Steel is all you want. All those other fancy coatings and colors are just mumbo-jumbo,hokem,snake oil, and hogwash. All designed to separated you from your money.

Gtamazing said:

Neither. High Speed Steel is all you want. All those other fancy coatings and colors are just mumbo-jumbo,hokem,snake oil, and hogwash. All designed to separated you from your money.

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For the consumer, that is 100% true IMO.

Most of the Cobalt, quenched in Unicorn Urine, Ultra turbo point, is all garbage.

A quality USA or Israeli (or equivalent) HSS drill will run circles around any Cobalt, Moly, TiN, etc. drill that you find at the hardware store.


[tl:dr version]

When you get to professional quality drills though, Cobalt most certainly does have a use. You can only really tell the difference after drilling a couple hundred holes at a depth of 6x the drill diameter in stainless steel.

The advantage of Cobalt is that it has higher heat and abrasion resistance without the brittleness and expense of solid carbide, but for general use, it also does not take quite the edge that good quality HSS does, so you're once again, better off with a plain old high quality HSS bit for most work.

The advantages of the higher grade materials only make themselves evident in a production environment, and even then the benefits can be questionable when looking at cost vs. lifetime.

Cobalt and moly are in the steel, not a coating. In technical terms, all HSS is high-moly, but M7 and M42 have more moly than M2 and M35. M2 is regular old HSS, M7 is high-moly HSS, M35 is cobalt and M42 has more cobalt and more moly, making it harder and more slippery. Titanium nitride (TiN) coating makes any drill more slippery but I don't buy into it myself, waste of money on that. Black oxide and gold oxide are pretty much the same thing, and useless. You really have to try hard to not get ripped off sometimes.

dankicksass said:

Cobalt and moly are in the steel, not a coating. In technical terms, all HSS is high-moly, but M7 and M42 have more moly than M2 and M35. M2 is regular old HSS, M7 is high-moly HSS, M35 is cobalt and M42 has more cobalt and more moly, making it harder and more slippery. Titanium nitride (TiN) coating makes any drill more slippery but I don't buy into it myself, waste of money on that. Black oxide and gold oxide are pretty much the same thing, and useless. You really have to try hard to not get ripped off sometimes.

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As mentioned above, each of those coatings has a place in a production environment, but unless you're an expert in tooling application, chances are you're wasting money with anything other than HSS.

I personally recommend bright HSS, I find it to be the best performer for general usage. Black oxide is fine and dandy, but while it protects against corrosion, it also increases the chance of adhesion.


I've been machining for my entire career, and still am rather dubious as to the benefits of all of the fancy coatings.

HSS, Cobalt, Moly, and Carbide are the only ones I can personally say for sure can have a large effect on tool lifetime, but that is only in a production environment.

When it gets to coated versions of any of those, TiN, TiCN, TiAlN, etc., I typically will leave that to the tooling experts at my suppliers, who are better qualified to determine the cost/lifetime ratio.

Thanks guess ill just go buy a couple of each and test them for myself.

They have their place.

I never use them in a hand drill unless I need to drill out a broken off tap or something that I cant fit in my drill press. They tend to snap if you arent careful.

Cobalts tend to be brittle and unforgiving but have their place for hard metals. Since they're brittle, they're best used in a drill press or production machine.

HSS is for everything else.

It's good to have both sets. Pull out the Cobalts when HSS won't phase the metal you're drilling.

I haven't used Moly.

If you go to MSCdirect.com they have an excellent chart on drill bits and their best uses.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1

Davefr said:

Cobalts tend to be brittle and unforgiving but have their place for hard metals. Since they're brittle, they're best used in a drill press or production machine.

HSS is for everything else.

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This is what I've always heard. You would only want cobalt if you were going to drill lots and lots of holes or if you were drilling through stainless steel. Moly doesn't last quite as long as cobalt but you don't have the brittleness to deal with. Both will last longer than a high speed bit.

filtered said:

Thanks, but that's not what i'm asking. I'm asking which is better cobalt or molybdenum.

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The Norseman site has a good explanation of the differences.

Why Choose Magnum™?

Substantially longer cutting life - The nitro-carburized flute has an increased Rockwell hardness.

Cuts harder materials - The flatter point takes a smaller chip. More torque is directed to a smaller area. This allows drilling into materials with hardness of over 30 on the Rockwell "C" scale.

Stops drill walking - The split point design gives accurate starting without the use of a center punch.

Holds tighter hole size - The split point design is self centering. This limits the normal oversize drilling characteristics.

Outstanding quality appearance - The rich amber gold color sets it apart from commodity cutting tools.

Runs cooler, uses less torque - 135° point takes a smaller chip resulting in less heat. Friction is reduced by amber gold surface treatment.

Stops chuck slippage - Flats on drill shanks allow easy positive chuck grip.
(Flats are machined only on Mechanics Length drill bits & Silver & Deming drill bits, not on jobber length drill bits.)
Magnum™ Vs. Cobalt

The Magnum™ drills will substantially outperform cobalt drills in work hardening stainless steel applications. This performance advantage is the result of construction differences between the two types of drills. Cobalt drills, manufactured to Type J NAS 907 specs, have a very thick web. This web is necessary to limit breakage of the brittle cobalt steel. Magnum drills are made of special hi-moly tool steel, which is much tougher than cobalt steel. The web on a Magnum drill can be thinned considerably due to the toughness of the steel.

A Magnum drill with its thin web will penetrate the work hardening stainless fast enough to continually cut beneath the chip which is hardening from deformation. This means the drill is cutting softer steel.

The cobalt drill, with its thick web, cannot be fed at a fast enough rate to cut beneath the area which is hardening. As a result the cobalt drill is continually drilling into hardened steel.

Stainless Steel: Work Hardening Vs. Free Machining

Work hardening grades of stainless are the 300 series with the exception of 303, which is free machining. Free machining grades include the 400 series in addition to type 303. A quick way to identify work hardening vs. free machining stainless is to observe the chip formation. Work hardening chips break up during the drilling process, while free machining chips are long and stringy.

Cobalt Applications

Cobalt drills are recommended for free machining stainless ( 400 series & 303), titanium alloys and other high tensile strength materials. These applications require the high red hardness of cobalt steel to counter the substantial heat generated in the drilling process.

the biggest drill bit killer is not using the proper Feeds and Speeds, A plain old HSS bit run at the proper SFPM and Feed Rate will drill more holes than a High performance Drill that is run at improper Speeds and Feeds.

Having said that I am Guilty of not always using the proper Feed and Speed.

To the OP: do you know how to figure out what SFPM to run drills?

Atlascycle said:

the biggest drill bit killer is not using the proper Feeds and Speeds, A plain old HSS bit run at the proper SFPM and Feed Rate will drill more holes than a High performance Drill that is run at improper Speeds and Feeds.

Having said that I am Guilty of not always using the proper Feed and Speed.

To the OP: do you know how to figure out what SFPM to run drills?

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filtered
What he said times 10.
Cobalt HSS is tougher than generic HSS, all things equal.
But speeds and feeds is the killer as mentioned here a couple of times.

The various coatings really don't come into play until you get involved in precision automated machining and then they get REAL important. Not hardly "smoke and mirrors" but not a significant factor with your 18V cordless hand drill.

Invest in a decent set of HSS bits, cobalt if you can get a deal, and SLOW DOWN. The most common drilling mistake of non-machinists is running too fast and/or misalignment. A couple of guidelines for amateurs using manual feed:
1/4" drill about 500 RPM
1/2" drill about 200 RPM
Coolant is a good thing.

A lot of the problem is i'm not using a drill press. So yes the speed and feed aren't perfect, it's not a perfect world. If this were for drill press only use I wouldn't even be asking this question. If i'm going to spend the money on some decent drill bits I want something that is going to be tougher than HSS. I need something that can hold up to hand drill use at odd angles and different thickness of steel.

Much of what i'm working on lately is far to large to take to the drill press, like a trailer frame and my Suzuki Samurai. The Samurai is getting some custom parts made like bumpers, rock sliders, traction bar, rear disc brake swap, roll cage, etc.

As far as coatings go I don't care about them. I'm only interested in the material the bit is made out of, not what's over it.

I have been looking at those Norseman magnum bits, which is why I started this question. Sure they sound like the bit I should be using, but that's according to their website. I wanted the opinion of someone that knows and has used both. I own HSS bits, they are fine for some things, but they **** for a lot of things. Could be that Dewalt bits ****, which they do.

If the moly isn't as brittle as the cobalt, then that sounds like the bit I should use.

Atlascycle said:

the biggest drill bit killer is not using the proper Feeds and Speeds, A plain old HSS bit run at the proper SFPM and Feed Rate will drill more holes than a High performance Drill that is run at improper Speeds and Feeds.

Having said that I am Guilty of not always using the proper Feed and Speed.

To the OP: do you know how to figure out what SFPM to run drills?

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this ^^^^^^^

filtered said:

A lot of the problem is i'm not using a drill press. So yes the speed and feed aren't perfect, it's not a perfect world. If this were for drill press only use I wouldn't even be asking this question. If i'm going to spend the money on some decent drill bits I want something that is going to be tougher than HSS. I need something that can hold up to hand drill use at odd angles and different thickness of steel.

Much of what i'm working on lately is far to large to take to the drill press, like a trailer frame and my Suzuki Samurai. The Samurai is getting some custom parts made like bumpers, rock sliders, traction bar, rear disc brake swap, roll cage, etc.

As far as coatings go I don't care about them. I'm only interested in the material the bit is made out of, not what's over it.

I have been looking at those Norseman magnum bits, which is why I started this question. Sure they sound like the bit I should be using, but that's according to their website. I wanted the opinion of someone that knows and has used both. I own HSS bits, they are fine for some things, but they **** for a lot of things. Could be that Dewalt bits ****, which they do.

If the moly isn't as brittle as the cobalt, then that sounds like the bit I should use.

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Then what you need is a good quality HSS bit set and make damn sure they are, and stay, sharp. Even if you are hand drilling, use a drill speed appropriate for the size bit. and for larger holes ALWAYS drill a pilot hole completely through the material. I don't know about the Dewalt bits, but I do know that a dull bit is nothing but frustration.

On your Sami are you building a rock crawler, a mudder or just a runner? (I've been doing Samurai stuff for over ten years; I have 3, an SJ410 (84) with a Swift GTI engine, and external cage, an 86 stocker for my son or daughter, (rebuild project) and a parts tin top)

Outlawmws said:

Then what you need is a good quality HSS bit set and make damn sure they are, and stay, sharp. Even if you are hand drilling, use a drill speed appropriate for the size bit. and for larger holes ALWAYS drill a pilot hole completely through the material. I don't know about the Dewalt bits, but I do know that a dull bit is nothing but frustration.

On your Sami are you building a rock crawler, a mudder or just a runner? (I've been doing Samurai stuff for over ten years; I have 3, an SJ410 (84) with a Swift GTI engine, and external cage, an 86 stocker for my son or daughter, (rebuild project) and a parts tin top)

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Rock crawler. I have a 94 with the stock 1.3 efi for now. It's SPOA on YJ's with 33's, 6.5:1 tcase gears and a bunch more, with a lot more that still needs to be built.

Looks good, if you are going disc in the rear, have you considered the vented Tracker rotors and calipers in the front?

Outlawmws said:

Looks good, if you are going disc in the rear, have you considered the vented Tracker rotors and calipers in the front?

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Thanks, but it's got a long way to go. And yes I have and already did the fronts. Once the rear discs are in, it's getting an Isuzu Rodeo brake booster and master cylinder. Should stop pretty well after that.

Atlascycle said:

the biggest drill bit killer is not using the proper Feeds and Speeds, A plain old HSS bit run at the proper SFPM and Feed Rate will drill more holes than a High performance Drill that is run at improper Speeds and Feeds.

Having said that I am Guilty of not always using the proper Feed and Speed.

To the OP: do you know how to figure out what SFPM to run drills?

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cs12/pieD or cs4/d