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Old 06-15-2008, 09:55 AM
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Let's talk drill bits.

Cobalt vs. Titanium.
I am looking at a few different sets which is better for general shop use. Mainly in metal. Thanks.

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Old 06-15-2008, 02:10 PM
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Quote:
which is better for general shop use. Mainly in metal
This all depends on feed rates, diameter and material being drilled, IMHO.
Here is a little tidbit though in regards to TI and Co drills...

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Q: Are cobalt drill bits coated like the titanium ones? If the cobalt bits are rockwell hardness 66 - 67 HRc, what hardness are the titanium bits? Once you sharpen a cobalt bit and the gold coating is gone, is it just a regular bit?

A: Cobalt bits are not coated, they are cobalt steel through and through. At the end of manufacture a cobalt bit is baked in an oven to turn the surface color of the steel a dull gold color. This is done primarily for easy identification by color. If the gold wears off or is ground off in sharpening on a cobalt bit, it is still solid cobalt steel. Our cobalt drill bits are made of M42 cobalt steel which has 8 percent cobalt content. The Rockwell is approximately 65.5 to 67 Rockwell C. Irwin titanium drill bits have a hardness of approximately 64.5 to 65.5 Rockwell C. The titanium coating is much harder at approximately 82 Rockwell C. If you sharpen a cobalt bit it is still as good as a new bit, assuming it was sharpened correctly. If you sharpen a titanium bit its performance will drop because the coating is gone on the tip; however, you still have the benefit of the titanium coating in the flute of the bit and on the sides of the bit. It will still perform better than a standard bit.
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Old 06-15-2008, 03:00 PM
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Thanks for the info.
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Old 06-20-2008, 03:05 AM
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Just to add to that- colbalt and tungsten-carbide cobalt bits are fragile compared to other high-speed steel bits. Because of this- they are usually confined to machine operations and limit hand drill use for most applcations.

Steel bits are coated with TiN, TiC, Ti(C)N, TiAlN, and other coatings to keep heat from building up and allow for standard bits to cut materal harder than the drill's base material would allow. Cobalt alloy bits can also be coated. Coatings provide increased use before the bit needs to be re-sharpened (with the eventual loss of the coating as given in above quote). These coatings really are helpful for preventing buildup when high speed machining in materials like Aluminum and cast iron, and are virtually a necessity when machining Titanium alloys. However, be aware that some alloys will react poorly to some coatings when machining- more a real problem with endmills.

If you have a drill sharpener-- standard high speed steel bits work well for most materials and are much less expensive and generally better for 'general' work where you'll need multiple diameters/sets. Speciality materials pay off on harder materials, long runs, surface finish, and higher speed machining.

As with most things- quality is the key, and quality usually costs.
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Old 06-20-2008, 06:16 AM
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I have a Drill Doctor and sharpen my drill bits as they begin to run or look dull. With hundreds of bits(accumulated before the sharpener and now all sharp again), this makes life with an electric drill a lot happier. A premium drill bit can last for years - though some Chinese and Korean bits that came with a supposedly top line complete letter, number and fractional set sometimes last one hole. I don't bother sharpening them - they get replaced.

Good standard steel bits and a sharpener work just fine - why pay the extra for exotics if you don't need 'em.
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Old 06-20-2008, 08:38 AM
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I always buy Hanson drill bits and most of the time I get the cobalt drill bits.
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Old 06-20-2008, 09:20 AM
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drill bits........

Hi,hands down,cobalt is the best,no comparison with the other types of bits,and titanium bits are a joke..
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Old 06-20-2008, 09:38 AM
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Originally Posted by boatbob2
Hi,hands down,cobalt is the best,no comparison with the other types of bits,and titanium bits are a joke..
Your absolutely right. You get what you pay for in drill bits...cheap ones are not worth it.
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Old 06-23-2008, 07:23 PM
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Many Titanium Nitride coated drill bits are poor quality high carbon steel bits with a fancy coating so they can sell for a higher profit.

True cobalt bits are very hard and are designed for high speed use in soft materials (i.e. Aluminum, copper, magnesium etc.) but do not perform that well in harder materials such as mild steel or cast iron.

Ideally you want a high speed steel drill bit with a black oxide coating for mild steel and cast iron, use cobalt for aluminum and other soft materials.

My opinion of TI coatings are they are mostly for looks unless you are using them in a manufacturing situation where it may allow you to use a cheaper drill to do the same job.

You may find that cobalt drills will chip along the edges when used in steel, this is because they are very hard and tend to bind along the edges in steel.

The best drill bit for general use in steel and cast iron is still a plain black oxide forged drill made by a reputable manufacturer, I tend to favor Cleveland drills but I know people find them expensive to buy initially.

In this day and age of cheap import tools I would suggest you stay away from "coatings" and look for a good quality drill bit that says it is made of high speed steel or "HSS".

Beware the drill sets marked as "HS" or high speed because this could mean anything the manufacturer wants it to mean. Of course any drill will make a hole and if all you need to do is make a hole for as little money as possible and do not care about hole size accuracy then the cheap import drill will do that for you, most people do not require the accuracy an expensive drill will give you...especially if your hand bombing through sheet metal with a hand drill.

Like all things there is a market for all these products, just don't expect your $9 fractional drill set to drill holes within 0.001" of size out of the box or drill three thousand holes in your machining centre and runout within 0.0005".
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Old 06-23-2008, 08:59 PM
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That's quite interesting, I had always bought Cobalt drills for drilling really hard material assuming that the harder cobalt was what was needed, however I also noticed they really did not live up to expectation when used for that purpose, what you are saying about them certainly makes sense now. Using Cobalt in a hand drill can also get quite expensive since they will break and chip so easily so I always used a HSS bit for that but I liked the coated bit when it was available, it is supposed to run cooler but I don't know that it really does though. I had very good service from Triumph Drill bits as well as Cleavland and the Cleavland taps and dies just can not be beat!
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Old 06-23-2008, 11:04 PM
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This is my fractional set, they are the best I've found so far. These are too aggressive for hand drilling. They will tend to triangulate the hole if you don't first use a center drill.

You do get what you pay for.

Another fav of mine is Norseman with a nitride coating. The flutes are back ground and are better suited for hand drilling.

Split tips are nice but are hard to re-create exactly like they were originally.
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Old 07-04-2008, 04:50 PM
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i'm a tool and die maker... been doing it about 20 years..


good quality cobalt drill bits are worth every penny.... i use cobalt bits almost daily on hardened h-13 tool steel at work... so i would say a good to high quality AMERICAN cobalt drill bit is awesome for home use...

the Dr. Doctor is a good machine if you cant sharpen a drillbit by hand and eye, and they do work good, i would recommend one to someone...


The titanium coating that people have talked of, at home its not needed, its generally good to have constant coolant flow on a tialn bit, and they work well on harder stuff also, but they arent needed at home...


I would recommend the regular to good quality cobalt set for home use, American made drills are better... Morse is the name brand i recommend..


If you have a good Tool Supply place in town, not harbor freight, or a place that sells hand tools.. i'm talking of a tooling supply outfit, that supplies machine shops and tool and die shops, go there to make your purchase, and you'll get a set of drills, a little more expensive, but, that will pretty much last the rest of your life...


I'm adding this... Always either center punch or center drill for starting your drilling, that alone will make your drills last longer.. also get a speeds and feed chart, if you know a machinist or tool and die maker, they'll have one, or you can probably find a printable chart online somewhere... drilling a hole isnt rocket science, but there are general guidlines to follow...

Last edited by Bru; 07-04-2008 at 05:19 PM.
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