Advice on drill bits for steel.

[tomas]

Hi all,

Any advice on finding bits that can drill through metal?

I've been making good progress, but I'm finding that drilling holes through steel is very time consuming. I need to make holes 5/16 in diameter and there-about. I've found a 5/26 cobalt bit for $10 friggin' dollars! With oil it seemed to make the drilling a little faster. I'm using a hand plug-in drill.

I hope to share some good progress on the hauling trailer soon!

For what it's worth, this Lowes link was somewhat helpful:

http://www.lowes.com/lowes/lkn?action=howTo&p=BuyGuide/DrlBtsBul.html

Any and all advice most welcome!

Thanks,

t.

[Radical Brad]

So far I have found that the cheap bits are useless, but the high cost bits are no better than the ones at the center of the price range.

When using the el-cheapo bits for drilling hub flanges, I usually tossed one out for each flange (~24 holes). The "deluxe" bits last for the entire process normally, and I usually break them by pressing too hard before the wear out. The last time I did flanges, I used the same medium quality bit for 2 builds... almost 100 holes!

I use vasaline as cutting oil. Just dip, and then drill.

Brad

[Zwolf]

I don't know about others, but I've just used to regular common drill bits with some oil. The only "special" thing about them is that they were the shallower bits... if that makes sense...? You know how some bits come to more of a point than others? Well, the others is what I used. Can't remember the angle name they had... But yeah, just those bits, some oil, and make sure to keep the bits sharp. Oh, and don't push to much. Pushing causes friction which will heat up the bit which will cause the bit to soften and then it's won't keep an edge.The oil helps, but won't keep it totally cooled.

[GregLWB]

So far I have found that the cheap bits are useless, but the high cost bits are no better than the ones at the center of the price range.

Brad

I have had the same experience as Brad. The one exception I have found are the step-drill bits from Harbor Freight. They come in a set of three and cut really well and seem to hold up too.:)

Greg

[trikeman]

Dittos on the HF step drills. Best thing since sliced bread.

[Locutus]

I bought a 1/8" black oxide bit from Home Depot for drilling screw holes in my Marauder's seat mount tabs. That's 24 holes in all, through 1/8" steel plate. The bit is still good, and I've used it for other jobs too. Cost was about 2 bucks, IIRC. Didn't see black oxide mentioned in the Lowe's article you linked to.

Good to hear positive feedback on the HF step drills. I was avoiding drill bits in general from HF because I didn't think they'd hold up. Looks like I was wrong about that.

Great "tip" on the Vaseline. :jester:

[graucho]

My opinion is if you are buying a buying a bit from Home depot/Lowes you need the black oxide or Cobalt Bits and also the package must say "for hardened steel" Also you CANNOT rev up the drill or drillpress enough to over heat the bit. Once the bit overheats its all over but the cryin. Speed is your enemy. Dont worry the bit will chew at a slower speed. A few drops of water while your drilling helps keep it cooler also.

[KoolKat]

I use Vaseline as cutting oil. Just dip, and then drill.
Brad

Hmmm...that explains why the container is missing.

[tomas]

Thanks for the advice, it all sounds good. I always thought revving up the drill would get me there faster..

HF lists a bunch of types of step drill bits:

http://search.harborfreight.com/cpisearch/web/search.do?keyword=step+bit&Submit=Go

Is it worth paying extra for the 'Nitride' coated bits?

t.

[John Lewis]

I'm still using ordinary high speed steel bits that I've had for years. Learn to sharpen them (Theres some info on Instructibles if you need it) and keep them sharp. I think Harbour Freight among others sell a cheap drill sharpening gadget for about $20 but you need a small bench grinder to go with it. I have one but prefer to sharpen off hand. Hand sharpening drills is a skill worth learning.

I usually spray a bit of WD40 for lube on heavier going. The bigger the drill the slower the speed needed. When using a hand drill I pulse the trigger to keep the speed down and use moderate pressure. If the drill won't cut it is blunt. Sharpen it. I once pressed too hard with a blunt drill trying to finish a hole. Drill broke, slipped and went through my finger. Needed a trip to casualty. That won't happen if you keep them sharp.

John Lewis

[GregLWB]

Thanks for the advice, it all sounds good. I always thought revving up the drill would get me there faster..

HF lists a bunch of types of step drill bits:

http://search.harborfreight.com/cpisearch/web/search.do?keyword=step+bit&Submit=Go

Is it worth paying extra for the 'Nitride' coated bits?

t.

These are the ones I got.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91616

Greg

[gbbwolf]

Well when I had my own drill press I made an automatic water cooler for it.
Just like the big industrial drills and saws use an automatic water cooler.

Easy enough to make a small electric pump, a screen, an old cooking pan or tray, and some tubing, On off switch.

Will keep bits at cool temp and never overheat and ruin a bit.

And best investment I ever made was a drill doctor that will sharpen up to 3/4" bits.

Nelson

[gbbwolf]

double post lol

[savarin]

Get good quality high speed carbon steel drills.
If possible get the ones that have a relief ground into the back edge of the cutting face. IE. if you look at the tip it has two edges on each cutting face.
Use a slow speed, the larger the dia of the drill the slower the speed.
Keep pressure just enough to bite, dont press too hard else the bit will flex and snap.
Always use some form of lubrication and cooling fluid.
I find ordinary engine oil works very well.
Back off the pressure as its getting close to breaking through till finished.
Cheap drills are a total waste of space.
I have a box of bit I purchased in 1974, except for the small dia bits I broke (in a hurry) they are still going strong.
The best drill bit sharpener on the market is
http://www.drilldoctor.com/product.asp?specific=138
Expensive but probably the only one that really works.
Its not too difficult to sharpen by hand, it just takes a little practice and if you can get someone who can show you it doesnt take long to learn.

[TheKid]

All of the above. I've been recommending the HF step drills for about as long as I've been on these forums. I use a 7/64" bit for a pilot hole first, because the step drills aren't always the best for starting holes. The 2 pc. set for $19.99 features much larger bits with thicker shafts, but the 3 pc. set for $7.99 is good for all around work. Buy a few sets, because the shafts can break. At any rate, for 16 bucks plus shipping, you'll have plenty of backup if you buy 2 sets. I use 7/64" bits for pilot holes because those are the bits to use for making flanges. A 1/8" bit is also good for pilot holes. You should always drill in "steps" whether using straight or step drills. For instance, for a 5/16" hole, Drill a pilot hole, then a 3/16" and then the 5/16". Your bits will last longer, and you'll need less pressure on the drill than if you start and finish with the larger bits.

[Wood Butcher]

I'll throw in my $0.02 worth, all of which is based on experience. Some may disagree, but like I said, these have worked for me. In no particular order...

Drill bit geometry is far more important than the coatings. Coatings (titanium nitride, or TiN, for example) cannot compensate for poor geometry. If the drill bit isn't ground properly (a lot of cheap imported drill bits fit this category) it won't cut worth a darn or at all.

Black oxide coating on some drill bits is there to prevent them from rusting. The sales pitch about "black oxide coating allowing the drill to run cooler" is partially true--a rusty drill bit will generate more friction and therefore more heat.

Drill bits with a polished or "bright" finish work just as well as black oxide coated bits.

Titanium nitride coating is really only helpful at high speeds and with plenty of lubrication. For the home user, TiN coated bits aren't worth the extra cost, IMHO.

Good lubricants for drilling and tapping are just about anything to cool the tool and help move chips from the cutting area. Some suggestions:

- General-purpose machine oil
- Motor oil
- Dark thread cutting oil used for threading iron pipe (sold in the plumbing department at big-box home centers)
- Vegetable shortening (dip the cutting tool in the shortening before starting)
- Lard (used like shortening, but make sure it doesn't go rancid)

Invest in a good drill sharpener. I'm partial to Drill Doctor as I have had very good results with their tools. If you purchase and older model on eBay, beware of the DD500 and DD750 Tradesman models--they are somewhat fickle about exact placement of the drill bits, but the Drill Doctor web site has updated manuals on how to place the bits correctly in the collets.

If you want very sturdy drill bits, look in an industrial supply catalog for "screw machine length" drill bits. These are shorter than the regular drill bits (known as "jobber length" bits) and able to stand much more axial thrust. Good places to look are MSC Industrial Supply or Victor Machinery Exchange.

Cheap drill bits aren't worth the gamble and are not good for much more than ballast. Good drill bits (usually those not made in China), treated properly, will last a very long time.

There are rare exceptions to the previous statement. I once purchased some Chinese drill bits that cut like demons once they were properly sharpened. Unfortunately they wouldn't hold an edge very long and quickly wore down.

Sharpen the bits after you use them. Sure, it can be a pain, but the drill will be sharp the next time you need it.

I hope this helps. YMMV.

Mike

[savarin]

You gotta agree 100% with all the above.
Step drills- never used them.
How easy is it to keep the hole straight?
Whats the thickest steel they can be used on?

[TheKid]

You gotta agree 100% with all the above.
Step drills- never used them.
How easy is it to keep the hole straight?
Whats the thickest steel they can be used on?


1. Yes. Especially about the coolants. In a pinch I've even used citronella which was very effective.

2. Step drills are easy to keep straight, as long as you don't put too much pressure on them. If you do and they go to one side, the shaft will snap. That's not much of a problem for the more expensive ones with a 3/8" shaft.
I used them to drill out a freewheel adapter, which is about 1 1/2" thick. I drilled out one side then flipped it over and finished from the other side. Not recommended if you want to use it again, because the two largest steps became dull. (I went from a 5/8" bore and drilled it out to 3/4"). For thinner steel up to 1/4", they're terrific IMHO. You can zip right through without changing bits. I do find however, the the geometry is lacking for starting a hole. I drill a pilot hole first with a good quality 7/64" or 1/8" bit.

[Zwolf]

In high school we used the used motor oil from the auto shop. It was a bit messy, but better than just trashing the stuff and we could still recycle our leavings when we were done with it.

[TheKid]

In high school we used the used motor oil from the auto shop. It was a bit messy, but better than just trashing the stuff and we could still recycle our leavings when we were done with it.


That's the Zombie way! Finally, people in authority who do things that make sense.

[madmike]

I used to use motor oil or transmission fluid for drilling and/or tapping lube.
Then I drilled a bunch of holes in the middle of winter. Working in the garage
in winter means the door is shut, which means there's no ventilation, which
means a really good buildup of fumes and aerosolized lube. It seems like that
stuff got into my lungs and stayed there for days, along with that stench of
hot motor & transmission. I'm pretty sure it's toxic and carcinogenic also.
So.
I dug up an old scented candle, and now I use candlewax as drilling and tapping lube. It smells much better, works just as well, and might actually be less poisonous(I hope.) I light up the candle and if using a hand drill just dip the
bit into the little puddle of molten wax, and for the drillpress I'll move the candle
up under the bit to lube it up. Seems to make less of a mess than oil, or at
least it's easier to clean up afterwards.

Oh, and I've found cheap drill bits to be worse than useless also, unless all
they ever touch is wood, plastic, or aluminum. Get the medium-priced ones
and learn how to sharpen them by hand. Offhand sharpening of drills and lathe tools is one of the most useful skills I ever learned, and I'm not even a machinist, I'm a fabricator.

[macka]

madmike,

I use cheap drill bits as guide pins for some projects, its cheaper then buying a piece of rod and cutting it, and you can reuse them too.

[TheKid]

I broke an HF step drill today, so I went to Autozone for some extra bits. I find they have some good quality bits at reasonable prices, and it's only a couple of blocks away. They also have step drills, 15 bucks a pop, but the shafts are much thicker than the HF ones. I dcided to try to start the holes with the step drill to see if they start better than the HF bits. It went through the steel like butter. I drilled six 3/8" holes and two 1/4" holes in 1/16" thick steel, plus one 1/4" hole in 1/8" thick steel in under 4 minutes.