Drill Bits...

[97SWBCHEVY]

Doh! I was using my drill set last night and realized I don't have cobalt bits. I have the Warrior titanium nitride set. Whatever, they cut. Then today I found Project Farm's drillbit test:

xc_hide_links_from_guests_guests_error_hide_media

Well alrighty then…I would’ve lost money if someone would’ve bet me that the DeWalts would’ve ranked first! Thank Ya Sir!

 

[97SWBCHEVY]

I have a set of those. They're cut OK, except that they're thick-web, "split point" bits, and I hate thick webs and split points. Manufacturers often use thick webs to make up for using crappy steel. The steel is brittle, so without a thick web, the bit shatters easily. In other words, the thick web is a cost-cutting measure because they can cheapen the raw material.

My "good" bits are USA-made, HSS, thin-web Government-Surplus from decades ago. Properly sharpened, they cut like crazy. Sometimes, they break. And the ones that get used, are getting pretty short from resharpening.

Thick-web bits are stronger, so they take abuse better...but they're harder to push through the material. To sort-of make up for that, they sharpen them by splitting the point. Duplicating that when re-sharpening is hateful. And I've seen brand-new, factory-sharpened bits that have crappy geometry; they don't stand a chance at cutting properly.

For the record, I worked in a production environment for thirteen years. The Company sent out the dull drill bits to an outside contractor for re-sharpening. (Hundreds, if not thousands of bits at a time, and 11/64 was hugely popular.) The sharpening contractor did such a piss-poor job (Drill Doctor, or similar) that when we got the "sharpened" bits back, I'd have to put them against a bench grinder to make them cut. In other words, I could re-sharpen the bits by hand on a bench grinder and make them better than the "professionals" could resharpen them using a fixture and diamond wheels. (Dumbasses put no relief on the cutting edges, so the bit resisted going into the metal.) It got so bad that eventually the company quit resharpening bits smaller than a certain size--they just bought new ones. I've got five pounds of used, dull but otherwise OK smaller drill bits that someday I'll get around to sharpening, that I took home from that company. They were going in the dumpster otherwise.

SHI TTY CHINESE BITS ARE NEVER GOING TO CUT PROPERLY. The steel is no good. A proper sharpening gets them to cut nice...once. If the hole isn't too deep.

If you see drill bits that have a little "pilot" point on them, for Fo ok's sake don't buy them. They're a gimmick. Good luck resharpening them. They're junk drill bits with a fancy, factory-sharpened end that can't be duplicated. Use 'em once or twice, throw them in the recycle bin. Garbage.

IF (big IF) the steel is good, a drill bit can be sharpened to cut and to last...but thick webs make that a challenge. Not impossible, but not easy, either.

In my experience, drilling mild steel, broken bolts, etc--it matters less that the bits are "Titanium" coated; or Cobalt; or whatever Miracle Technology. The common stuff is made with cheap steel, thick webs and split points, and they don't work as well as a QUALITY HSS thin-web bit that's been sharpened properly with some relief on the cutting lips.




As others have said, don't sneak-up on the final hole size by drilling progressively larger. Select your final drill bit size. LOOK at the web of that bit. Select a pilot bit just a hint larger than the web. Drill the pilot hole, drill the hole "for real". Two steps--not five, or three, for any drilled hole likely found in automotive work.

Thank You Sir for sharing your knowledge… I rebuilt cylinder heads for about 8 years at my uncle’s shop, the majority of which where 4 cylinder aluminum heads and I’ve drilled out more broken exhaust studs than I can put a number to…and if I ever have to drill another one out again it will be too soon! Lol
The one thing I could never get a handle on was sharpening a dull drill bit…and I tried over and over and over again…we bought 2-3 different brands/styles of “sharpeners” and none of the bits would cut any better than they did before…granted none of them were “high end” drill bit sharpening set ups, and very little money was invested in them if you know what I mean…lol but I wasn’t any better at sharpening a bit on a stone, and I was trying to sharpening on the valve grinder with about as fine of a stone as ya can get… I think one of the main problems was I never tried sharpening a bit until I had dulled the crap out of it…
Any tricks you could pass on???

 

[thegawd]

I learned how to sharpen anything in highschool machine shop class. we funded our own supplies and had everything. that also ment we had to maintain our cutting tools instead of just replacing them. everything is sharpened on a bench grinder. look at a good bit and then mimic it on the bench grinder. be quick and what you do on one side has to be done to the other side. theres two things that need to be done, the cutting edge and then the trailing edge where the shaving will go. its quick and easy but takes patience and LOTS of practice. the larger the bit the easier it is to understand what to do.

I'm sure theres a youtube video on it...

 

[Frank Enstein]

I use a Drill Doctor and it works well for me. I can sharpen bits 3/8" and up but I don't see well enough to do smaller bits anymore.

 

[kennythewelder]

When I was a young man, an old man thought me how the sharpen a drill bit by hand, on a bench grinder. That was over 45 years ago. Been doing it that way for that long. Only the very small bits re hard to do because of the size and trying to put the correct angle on something so small. I can still do it, but in my old age, it's hard to see that small fine point. I am talking about the smallest bits in the set, only.

 

[Erik the Awful]

I've used a Drill Doctor, but it really only worked on the larger bits. I've had bits start to dull and I've used hand files, bench grinders, and angle grinders to sharpen them on the fly. I've probably done it "wrong" more than I've done it right, but they cut the right sized hole and I didn't have to replace the bit.

 

[Frank Enstein]

I've used a Drill Doctor, but it really only worked on the larger bits. I've had bits start to dull and I've used hand files, bench grinders, and angle grinders to sharpen them on the fly. I've probably done it "wrong" more than I've done it right, but they cut the right sized hole and I didn't have to replace the bit.

Me too! Great minds run in the same gutter!

 

[96TahoeDoug]

After drilling a thousand holes into stainless unistrut and 500 into concrete including rebar I got a feel for the art and lubricant, pressure, speed and Bosch bits seemed the best overall.
I make knives and this helped understand the cutting edge and keeping that intact and sharp.

Drill slow with minimal pressure and use a cutting oil. Vary speed and pressure to get a nice cut going and hold steady. Keep it cutting. Do not overheat the tip. Avoid coloration as a primary rule. Any color is altering the temper and hardness . Cool immediately in water if it's smoking your oil. Colors is bad - blue is softest and wheat is hardest and I won't argue that just slow and lubricated to avoid color = sharp bits.

 

[96TahoeDoug]

After drilling a thousand holes into stainless unistrut and 500 into concrete including rebar I got a feel for the art and lubricant, pressure, speed and Bosch bits seemed the best overall.
I make knives and this helped understand the cutting edge and keeping that intact and sharp.

Drill slow with minimal pressure and use a cutting oil. Vary speed and pressure to get a nice cut going and hold steady. Keep it cutting. Do not overheat the tip. Avoid coloration as a primary rule. Any color is altering the temper and hardness . Cool immediately in water if it's smoking your oil. Colors is bad - blue is softest and wheat is hardest and I won't argue that just slow and lubricated to avoid color = sharp bits.

Angle grinder with flat side of cutoff wheel to sharpen bits. Two presses on the semi flats two more at the cutting edges done. It's time and pressure at the same angle. If it doesn't work magnify the surfaces, note your attack, retry. Sometimes a vice others my hand to grip. Any fine grit belt sander is great two.

Takes max 5 seconds to make the 4 grinds sharpening the bit. Boom boom boom boom done.