'K, the title is the question. What makes a drill bit keep a sharp edge for a long time? I know better than to buy the el-cheapo chinese/taiwanese import crap at Harbor Freight, but how do I know the expensive stuff is really any better? I see a lot of "titanium coated" bits around. What the hell does that do? Better than black oxide? And, btw, "black oxide" of what, exactly? I just want a bit set that will punch lots of holes in mild to medium hardness steel without going up in smoke. So, what are the technical attributes to look for? And, lacking that kind of genuine technical knowledge, what brand is best? Reasonably priced? :seeya

[posted in OT, got no response. :( ]

 

Good question, I would like to know too. :lurk:

 

The best commercially available bits are cobalt alloy. Just look for the word "cobalt". They're more expensive than standard bits but last a lot longer. Next best would be "HSS" (for high speed steel). Keep the hole lubricated with oil while drilling and let the bit cool if smoking occurs.

 

Well, over the decades I have drilled lotsa holes in all sorts of materials...and so with modern tech, it depends on what you are doing....IF you working with a lot of square tubing, you may want to buy a set with built in pilot bits tips....
years ago, they were used allmost exclusively on plastic, like Lexan, but today they have found multi uses....shop HDespot for DeWalt set in the american 1/64 to 1/2 , NOW, over the years HUOT (sp) in the grey steel index box, made the same set in standard bits...black steel...they last a LONG time IF properly treated, are not as aggressive on the cut as the Dewalts above, but still need lotsa oiling if you do hard/thick enough steel....
I try doing most of my drilling on a drill press, so to make crap easier....just better all around...my press is as tired as I am, at 20 ++ years old now....

for the wire gauges, I find the bits from 60 to 1 handy also, but they are HARD to find individually to fill the inevitable broken tooth in the set....

then if you heavy into crap, the letter sets are helpful...but you getting into Machinest territory now....

then again if you want METRIC....well have fun....you need a machinest size screw/drill/gauge thread deptch chart.....if you working steel...I find one size larger on the drill size is SO much easier in tapping the hole..., damn steel is TOUGH.....

and YES I forgot, cobalt is nice, but note the price too, still the only way a bit survives on steel, is OIL, with maybe water for cooling, making that OIL has to be Lanoline based...cutting oil...

but for onesey twosey type homeowner crap,....WD40 will work as well, just keep it wet....


GENE


[Modified by mrvette, 10:57 AM 6/23/2003]

 

So, Gene, you're recommending the DeWalt brand? That would be good to know, since those are not too expensive at the ol' H.D. I've always been a little skeptical :skep: of the DeWalt brand, since they're made by Black & Decker ("PeckerWrecker") :D

 

The ones that have passed the test of time for me are quality brand name
HSS bits (like Vermont American). I have some that have held up to 'homeowner abuse' for years.
Sometimes needing a sharpen - but rarely breaking.

Those 'Drill Doctor' sharpeners look cool - but I can't bring myself to spend the $$ on one.

I want to hear Norval's suggestion. He has clearly drilled more holes than anyone here !!

:seeya


[Modified by NHvette, 11:04 AM 6/23/2003]

 

NH, Hey wait a minit, I"v drilled a few holes myself too....

OH wait a minit,,....

dont mean to hijack a thread.....

GENE :D :D :D :reddevil :reddevil :lolg:

 

OK, now there's another question: Are drill bit sharpeners (of the affordable home shop variety) any good? I've always assumed they'd be fine for wood work, where a hardened edge is not critical, but I figured for cutting steel you've got to have some kind of super-hard edge that would be ruined by any kind of attempt to sharpen it. Am I wrong on that? Enquiring minds want to know! :crazy:

 

I'll second much of what mrvette said.

Being a diemaker I've had my share of drilling experience. HSS bits are dollar for dollar your best best. I imagine you're talking about common automotive parts type drilling. Few if any of these items are hardened, so exotic bits are not necessary.

As for sharpening, if you have a bench grinder you'd be all set. It's a matter of sparking one side at a time on the 117 degree angle..eyeball your cut to insure you've sharpened so the leading edge is the high point...then scale measure your cut, and do the other side..maintaining equal edge dimensions. Finish by putting a slight almost vertical cut to the leading edge so you don't have that razor edge line which will break down fast.

For cooling a deep hole project, a mix of light oil and water is de'rigor.

BTW--drill rotational speed and downward pressure affect not only the quality of the hole but the life of the drill edge. You should always adjust so that you get a even curl chip. This usually indicates a best match for the drilll and material. Most people apply too much rotational speed which heats up and wears down the drill edge real fast.

Another BTW--***** punch your center before drilling.

[quote]posted in OT, got no response.[quote]
I'm not surprized. :rolleyes:


[Modified by biltogo, 12:05 PM 6/23/2003]

 

:iagree: Excellent advice !!!


gman

 

Get a DoAll catalog. Top quality.
I have no trouble with HF.
i buy 10 packs for $2 and throw them away when they get dull.

 

:iagree:

I've have titanium bits not survive 1 hole because of too much speed and no cooling/oil

Steve

 

Forget the coating. Get good Vermont America or DeWalts (expect to pay $40)

 

The proper rpm and a little cutting oil make a world of difference. You can get a good cutting oil from places like MSC, I use the LPS brand. As far as drill sharpeners, I've used the Darex versions $2500, $1100 and the $125. The $1100 version is my favorite, my dad has the $125 version. The cheaper Drill Doctors would be a good addition to a set of quality bits.

 

Are you sure they are only titanium coated? I think a good set are titanium alloy and have nothing to do with the coating. They are just packaged that way to look good but under that coating is a good drill bit. I know guys who swear by them.

 

i personaly like Dewalt Titanium :yesnod:

 

I have used HSS bits for years. Either dry or with oil depending on the job and the location. Mostly in steel or cast iron. I was taught at trade school to sharpen by hand and eye on a pedastal grinder so I never got to use a drill fixture. I was a field service tech for years so we had to make do with what we had on the job.
Check MSC but stay with American made vs import for a better quality product.
Gary

 

I find that just going really slow, having the bit moving as slow as possible yeilds good holes and long bit life. A lot of the time I don't bother with cutting oil, as long as the bit is removing material (in a long spiral is best) it isn't dulling. As soon as doesn't, it dulls.

 

http://www.dewalt.com/us/products/ac...categoryID=239
These are top of the line DeWalt and they are only titanium coated. I think pure Ti it too weak. (steel is stronger, but heavier)