Are there better drill bits than cobalt?

[ME 109]

Where do you work that has this stupid gotta-have-been-made-by-a-lawyer rule?

A rather strong vehicle manf.

[Zombie Master]

I hate the throw away system. But hell, I can't seem to get a year out of a toaster oven anymore!

It's not you, it's the toaster oven.

Thanx man....I was gettin' worried.

[Zombie Master]

Purchase good industrial grade drill bit, forget anything sold by home centers. I perfer Black Oxide bit.

In my job as maintenace manager I purchase hundreds of drill bits a year, worth the extra money to get good bits. Cheap bits dull quickley can break off in the matterial and in general don't work very well. You get what you pay for.

As for sharpening drill bit forget the mechanical drill sharpeners, I have yet to see one other then an industrial type that worked worth a damn. Most of the home owner sharpeners sharpen the bit with a twisted back rake, you what your back rake to be flat.
Learn to sharpen bit by hand on a grinding wheel and you will suprise how well they cut, just make sure to quench the bit offen and not allow the bit to get hot, turn the steel a color and the bit is now junk. Again you need a good wheel, most that come with bench grinders are junk. You need to dress the wheel to make sure you have good cutting (grinding) surface.

When I was in the USAF as a machinist I could sharpen a #30 bit on a wheel chucked in a home made spindle in my pnumatic drill. Holding the drill between my feet running the trigger with the toe of my boot and bent over sharpening drill bits. I sounds difficult but it was easier then the 4 mile trip off the flight line to the shop to restock my tool bag.

Black Oxide: is that better than a good quality cobalt bit?

I guess I should invest in a better wheels for my grinder. Will one medium do the job?

[richard t]

I use Lawson bits at work, high priced but worth the money, Greenly is another good brand. Your bit needs to be a bit harder than the metal your're drilling

[Major Softie]

Black Oxide: is that better than a good quality cobalt bit?

No. Black Oxide is just one of the coatings (the cheapest) found on HSS bits. He was just saying that he buys the simplest coated HSS bits, but only in high quality versions. You can get a 64-bit set of Black Oxide bits from Harbor Freight on sale for about $15, or you could spend over $100 for the same thing from a premium manufacturer, and there's a whole lot of steps in-between. There is a very real difference in quality in bits that have exactly the same "specs."

[Zombie Master]

Black Oxide: is that better than a good quality cobalt bit?

There is a very real difference in quality in bits that have exactly the same "specs."

and that's......not OK

[Ken in Oklahoma]

For those interested in the subject there's a wealth of information on the internet, including U Tube videos. Google [sharpen drill bits] or something similar and all will be revealed.

Editing: Be aware though that some of the information is crap. For example, one article suggested grinding the bit to rough sharpen it, then finish with a file! Huh? A quality High Speed Steel drill bit that is properly hardened and tempered won't be susceptible to filing.


Ken

[Curt Henry]

When drilling speed (RPM) of the drill is very important, rule of thumb (4 X Cutting Speed of Material)/diameter. It's been 40 years from when I went to VoTech for Tool and Die, if my foggy memory is correct the cutting speed of mild steel is 100 and none sticky aluminum alloy is 400. Then there is rate of feed, small bit light feed large diameter bit heavy feed.

Drilling a 1/4" (.250) hole in mild steel
(4 X 100) / .25 = 1600 RPM

Run the bit faster, you will over heat the bit and loose the temper (soften) of the steel.

Sharpening bits by hand, replace the crap wheels that came with your grinder with good Aluminum Oxide wheels and keep them dress to provide a good sharp cutting edge, to prevent burning of the item your grinding. Norton makes very good wheels.

[30yearoldjunk]

A fellow rider and tool-and-die maker told me the 2 most difficult jobs, or those requiring the most skill, in a machine shop, are sharpening drill bits and rolling steel.
I tell myself that every time I butcher a drill bit on the bench grinder.

[Major Softie]

Editing: Be aware though that some of the information is crap. For example, one article suggested grinding the bit to rough sharpen it, then finish with a file! Huh? A quality High Speed Steel drill bit that is properly hardened and tempered won't be susceptible to filing.
Ken

LOL. Maybe a diamond file?