ruining all my drill bits

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I'm working on a large project that requires a lot of drilling into 1/8" mild steel.  For some reason, I am ruining all my drill bits on these pieces, which has never happened to me before.  First, I know what you're thinking- I AM using cobalt bits.  The holes are 5/16" and 1/4" and I'm center punching them first, then drilling a small pilot hole before using the large bit.  I use cutting oil, but still the bits seem to only work for literally one hole and then just spin.  I don't want to invest in a drill press, so I'm just using my Bosch hammer drill (not on the hammer setting though).  I suppose I am probably drilling too fast (the drill is variable speed), but I don't think that alone could explain why they're being dulled so quickly.  Does anyone have any idea why this could be happening?  Is there a different type of bit I could purchase that would last longer?
Reply:You should be able to drill those size hole with no problem even without a pilot hole but I know it makes it easier with a hand drill. The only thing that seems reasonable is a too high drilling speed.
Reply:First, you need a coolant, not a cutting oil.  Get water-soluble oil, and mix in a squirt bottle.  There are also several commercial coolants, that are less messy, that work good.For the size holes you are drilling, doubt that drill will spin too fast.  Correct down-pressure is also important, if you're not pushing down hard enough to cut, the bit just sits there and builds up heat.I'd generally be using a good brand of regular industrial high-speed bits.Do you know how to sharpen bits properly?
Reply:I should have mentioned the DeWalt drill bits that drill a pilot hole and then cut the outside of the hole first. I can't remember the trade name but they are the same as the old B&D Bullet Bits. They are the best bit I have ever used for thin material.
Reply:At first I thought my bits were just cheap, but I've used both Bosch and Ridgid cobalt bits and they only ever last for one single hole.  I am applying quite a bit of down-pressure as the workpiece is on a concrete floor, so I'm basically on top of it pressing down.  I never thought about coolant, always assumed cutting oil was what I needed, but will look into that.  Can anyone link me to some instructions on sharpening bits?  I've never done this before...Even still, I shouldn't have to be sharpening them after every hole for 1/8" mild steel.  The only reason I can possibly imagine is that since I'm using a hammer drill it's max speed is way too fast for metal, but even this seems unlikely.
Reply:Personally I never liked the Bosch bits that I have used. They don't seem to hold up as well as others I have used. I agree 100% with you oldtimer the B&D Bullet bits are my #1 choice in my hand drill 90% of the time. I also forget what the Dewalt ones are called. The only problem I have had with those bits are when drilling thru multiple layers. The bit cuts a washer as it exits the 1st piece. If not removed or if the pieces are not super tight the bit just spins gets hot and wipes out fast.Most of my non bullet bits are just plain HSS. The basic set on the rig are Hitachi's but I have 2 or 3 boxes of misc brands around the shop.I'm also thinking you are running the bit to fast, but the oil may be cauing the slipage also. Remember if working on the floor, that the concrete will destroy that bit if it hits the floor. Put a piece of scrap 2x under the steel to protect the bit after it goes thru or set the material on blocks.There are jigs to use on a grinder to sharpen bits. I never got good at it on small bits, big ones turn out so so.. Drill Doctor is a drill sharpener that works quite well. I have a friend with one and if I remember to bring the bits does a good job on standard bits. The kits starts at about $70 and go up. I use big bits so I would need the one that goes for about $150. A bit to pricy for occasional use for me. I dont dull enough bits to justify the cost. Most of the time they snap.Last edited by DSW; 05-20-2008 at 12:28 PM.
Reply:Ding ding, we have a winner!  The bits hit the concrete every time.  I started out using masonry bits and they actually lasted longer, so this is clearly what is going on.  Thanks DSW!  I would still like a tutorial on sharpening, though, if anyone can point me in that direction.
Reply:This here, right now, is a real good spot for somebody to post a really sarcastic comment
Reply:Originally Posted by zachDing ding, we have a winner!  The bits hit the concrete every time.  I started out using masonry bits and they actually lasted longer, so this is clearly what is going on.  Thanks DSW!  I would still like a tutorial on sharpening, though, if anyone can point me in that direction.
Reply:Originally Posted by zachDing ding, we have a winner!  The bits hit the concrete every time.
Reply:I can't give a tutorial, you really need a video or personal instruction,,,,,,    best way I can describe it is, using a standard bench grinder, holding the drill bit flat and square to the table, but at the correct angle of the cutting edge, you hit it, and immediately push down on the part you're holding, twisting clockwise at the same time, thereby driving and turning the bit up on the grinding wheel.  Perhaps there is somebody here that can describe better than I ,,,,,,    BUT, if you're only going thru 1/8" steel, NOT INTO CONCRETE, you should be good for hundreds or even thousands of holes .....
Reply:If you watch your chips, you will know if cutting oil or coolant is needed.  If they are shiny.  nothing is needed.  If they start to turn blue, a little oil or coolant will allow you to drill faster.  I use an aerosol penetrating oil.  Thicker is better.  Thunderbolt, Thrust, PB Blaster.Coolant keeps the chips silver, lube gets you through that last little bit.To sharpen a bit:LOOK at a new one to see the angle of the cutting edge.On a grinding wheel, hold the bit so the cutting edge is up and parallel with the wheel.Put the bit up to the wheel, Grind the edge so it has no round spots.  Do this gently, or dip it in water every few seconds.Go slow DON'T turn the bit blue.Once the edge is cleaned up, move the bit UP the wheel still gringing and holding at the same angle.  Go slow. When you get up a ways, look at the bit.Do the other side the same way with the same pressure and timing.Compare your bit to the new one.  Just keep at it, as you do more and more, you will get better.  I learned how to sharpen a bit when I was drilling truck frames mounting dump bodies.Have a blast!David David.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by zachDing ding, we have a winner!  The bits hit the concrete every time.  I started out using masonry bits and they actually lasted longer, so this is clearly what is going on.  Thanks DSW!  I would still like a tutorial on sharpening, though, if anyone can point me in that direction.
Reply:Zach, it's dead simple. I had a whole bunch of blunt drill bits. I was going to buy one of those drill sharpeners. Then I picked up a cheap ($20) grinding wheel. It took about a minute to sharpen each one. You'd have to be a dill to stuff it up (though you were drilling into concrete - there's that sarcastic comment, Mark. I couldn't resist it) Not sure I would bother sharpening 1/8 bits, though. They only cost a dollar or so.Scott
Reply:That concrete will get em everytime!!  When sharpening the most common mistake I see is people not getting the trailing edge lower than the leading edge.  You do that and keep the right angle and you'll be good.  Oh, and quit hitting the concrete!DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:I have drilled as many as 200 holes in 1/4 inch plate with ONE 1/4 cobalt drill bit.Make sure you are applying some pressure.Are you using a drill press???Do not center punch the plate because that work hardens the surface.Just drill the plate. If the drill bit walks it is not sharpened correctly OR the drill is not perpendicular to the work surface.
Reply:I've tied to hand sharpen drill bits many times. If you can get the exact angle on a sharpened bit as a new bit, you must be a genuis. I have never had luck with that.Last x mas i recieved a drill dr. bit sharpening kit as a gift. Once i got the hang of centering the bit correctly in the chuck, all my medium size bits are now sharp as new. The chuck does not center the smaller bits properly which means the kit will not sharpen the smaller bits properly. However, the medium size bits it works well on. This was a great tool i can use for a long time.
Reply:Originally Posted by zachI'm working on a large project that requires a lot of drilling into 1/8" mild steel.  For some reason, I am ruining all my drill bits on these pieces, which has never happened to me before.  First, I know what you're thinking- I AM using cobalt bits.  The holes are 5/16" and 1/4" and I'm center punching them first, then drilling a small pilot hole before using the large bit.  I use cutting oil, but still the bits seem to only work for literally one hole and then just spin.  I don't want to invest in a drill press, so I'm just using my Bosch hammer drill (not on the hammer setting though).  I suppose I am probably drilling too fast (the drill is variable speed), but I don't think that alone could explain why they're being dulled so quickly.  Does anyone have any idea why this could be happening?  Is there a different type of bit I could purchase that would last longer?
Reply:Ummm, zodiac, he already figured out why he was trashing the bits after each hole.It's because he had the steel plate lying on the concrete floor, and as soon as he drilled through the steel the bit destroyed itself on the concrete underneath.And cobalt bits are  typically NOT coated bits, but are made with a hard cobalt-alloy steel and hence are cobalt (steel) bits.The gold-colored Titanium bits ARE coated, with a titanium nitride coating.  If the factory puts the titanium (nitride) coating on a cheap steel bit, all you have is a fancy gold-colored cheap bit.A drill press has several advantages, including (usually) different rotating speeds, and also (hopefully) the ability to keep the bit straight (or at the desired angle) and not wiggle or change orientation as you drill the desired hole.  Also the factor of clamping the workpiece to the table and not having to worry about the work or the drill (motor) torquing or twisting around when a bit snags in a hole.  And the ability to more carefully apply the desired downforce as you drill the hole.  etc, etc.
Reply:Takes a bit of practice, a fine grinding wheel and a drill point gauge.Drill point gauges are available from mcmastercarr.com and others.Don't forget to back grind (lip clearence) or the bit won't cut.See: http://www.mmsonline.com/articles/068901.htmlThanks,Jim
Reply:I've used compressed air to help keep a bit cool.  It actually works great, even on hole saws.  When you have a very small tip of the bit toucing anyway, friction isn't all that great, but can build up some heat.  This heat weakens the edge and causes it to dull.  Therefore, by keeping temperature down, you can make the bit last longer.  In short, heat is the killer, and the result of friction.  Although you can't do much to reduce friction (since the surface contacting is so small), you can keep heat down.I have even submerged items in water to drill them.  It is the best method I've found, but not always practical.
Reply:Really need a machinest to chime in on this but I believe drill bit speed is figured in feet per minute on the outer edge. To make things simple there are charts that show this as rpm's for each size bit. The bigger the bit ,the slower the rpm's.As mentioned air, cutting oil, and soluble oil can be used as coolants. Tap Magic is great and I used to use it with Hougen (?) bits when drilling metal I was going to mig weld because it evaporated. I wasn't paying for the high priced stuff. Someone will probably slap my hands but WD-40 worlks real well too.
Reply:The speeds and feeds are a bunch of formulas and mesmerization that will tell you exactly the right speed and feed for any given job.For hand drilling, just go slower... with WOOD for backing! Now get back to your sharpening practice, your gonna need the skill of hand sharpening bits anyway!  No, no, WD-40 works just fine O.T.!Last edited by tanglediver; 05-23-2008 at 01:43 AM.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:we use a mixture of soap and water, in a spray bottle. it cools real good and is cleaner than oils or hogwash.
Reply:Some people will hate me but, what about the $30 drill press from harbor freight? You won´t regret it. When you´re drilling with a hand drill you make the bit wiggle some and this hurts it. If you´re making many holes alike a drill press will help you out a lot. I have it, done 100th´s of holes and this stuff rocks! and for 30 bucks you can´t go wrong!And all mentionned above too My Babies: HF Drill pressHF Pipe Bender3   4.5" Black and Decker angle grindersLincoln Electric PROMIG 175that´s it!Originally Posted by EngloidI've used compressed air to help keep a bit cool.  It actually works great, even on hole saws.  When you have a very small tip of the bit toucing anyway, friction isn't all that great, but can build up some heat.  This heat weakens the edge and causes it to dull.  Therefore, by keeping temperature down, you can make the bit last longer.  In short, heat is the killer, and the result of friction.  Although you can't do much to reduce friction (since the surface contacting is so small), you can keep heat down.I have even submerged items in water to drill them.  It is the best method I've found, but not always practical.
Reply:Something I have found is using a pilot hole too big,  this puts too much pressure on the corners of the cutting edges and makes them chip almost as soon as the drill hits the hole.  An engineer told me to never use a pilot hole bigger than one third the size of the next drill.
Reply:Originally Posted by sheppardSomething I have found is using a pilot hole too big,  this puts too much pressure on the corners of the cutting edges and makes them chip almost as soon as the drill hits the hole.  An engineer told me to never use a pilot hole bigger than one third the size of the next drill.
Reply:i just had the same problem i was drilling through 1/2" holes in 1/4 in angle. I would drill onehole and the bit would be done. But i just returned the bit and said it was defective. If you pay $15 for a drill bit and it only drills one hole to me its defective. I was using lubrication and drilling at slow speeds so ,  After trying various bits the Rigid american made cobalts were the best that i used. Go figure the Chineses ones were worthless