Drill bits for metal and using them properly

[Wilhelm]

This is what I know as a "crosscut" point.
Other manufacturers may call it differently though.

A crosscut point ground drill bit has much less core friction resistance and takes a better bite starting the drilling process.
The bigger the drill bits OD the more beneficial this grind gets, unless You utilize a pilot hole then it doesn't matter.

 

[Wilhelm]

Almost daily.
Me neither

Great!
Let me know if You happen to run out of something and I'll see whether I can get You sorted.

 

[Wilhelm]

1/2" Solid-Carbide crosscut tip drill bit, mild steel alloy workpiece, no cooling, no pilot holes - drill bit didn't even care, just made a hissing sound eating into that steel block.
High rpm and high feed with chip breakage - the generated heat transfers greatly into the workpiece steel chips.
Machine processed, not freehanded.

 

[Wilhelm]

The larger the drilling operation, the slower I go

2nd R.O.T., the larger it is, the wetter I keep it

To me, you can NEVER have too much cutting fluid, it doesn’t hurt anything to have a bath of cutting fluid on it. The cleanup is a different story

Nah, punch it!

True!

And true!

Solid-Carbide tooling and ISO 12.9 grade bolt steel workpiece (way over SAE grade 8, or a tad over grade ASTM-A574).
All the cooling the machine is able to supply and wouldn't want it any other way!
At the rpm's Solid-Carbide tooling calls for a lot of the coolant is just flung off and away, every drop counts for a productive tooling lifecycle.

 

[Wilhelm]

Surprisingly few replies on this topic.

Either I killed the thread or no one uses drill bits.
If it's the former, my apologies!
If it's the latter I bet asking advice on sharpening a chainsaw chain would have resulted in a 100 page thread by now.

 

[Moparmyway]

Surprisingly few replies on this topic.

Either I killed the thread or no one uses drill bits.
If it's the former, my apologies!
If it's the latter I bet asking advice on sharpening a chainsaw chain would have resulted in a 100 page thread by now.

I like sharpening my drill bits, and they cut, but I’m definitely saving your pictures and I will be copying you !!!

 

[Wilhelm]

I like sharpening my drill bits, and they cut, but I’m definitely saving your pictures and I will be copying you !!!

Erm

PATENT PENDING ! ! !



That's cool, I like that!

 

[Wilhelm]

Here the use of 70+% rubbing alcohol works better when drilling and tapping aluminum.

Aluminum really likes to "stick" and oil or diesel helps only moderately.
I need to try alcohol!

What rpm is best for 1/2" and larger? I haven't tried 200rpm (the minimum of my drill), and I rarely drill larger than 1/2", but I feel like it could get quite hot at 200rpm with large bits.

RPM selection depends on tool type and OD as well as workpiece material being processed.

1/2" HSS(Co) in mild steel 250-400rpm, high alloy steel under 250.
Whenever You are uncertain which rpm to choose start low and increase if the bit is biting and the chips aren't blueing.

 

[Wilhelm]

I like sharpening my drill bits, and they cut, but I’m definitely saving your pictures and I will be copying you !!!

I'd love to write "send me some dull bits and I'll give them a lick", but shipping cost both ways would make it a futile endeavor.

I need to take more pictures of my grinds.
Maybe make a video?

 

[jacob j.]

Surprisingly few replies on this topic.

Either I killed the thread or no one uses drill bits.
If it's the former, my apologies!
If it's the latter I bet asking advice on sharpening a chainsaw chain would have resulted in a 100 page thread by now.

I use the bits you gifted me a couple years all the time - Low speed and lots of cutting fluid. They've done a phenomenal job.

One of your bits modified a new-old-stock Carlton bar so I could run it on a Mac 125.

 

[ray benson]

View attachment 358508

This is what I know as a "crosscut" point.
Other manufacturers may call it differently though.

A crosscut point ground drill bit has much less core friction resistance and takes a better bite starting the drilling process.
The bigger the drill bits OD the more beneficial this grind gets, unless You utilize a pilot hole then it doesn't matter.

I have called that a split point. I hand sharpen and use a Drill Doctor. But want to try that special grind you showed on the previous page.

 

[huskihl]

I learned how to sharpen drill bits in shop class 40 years ago, but just enough to make a dull or broken bit cut again in mild steel. I can’t imagine grinding one to hold up to a grade 8 bolt for multiple holes. Wife picked up a Drill Dr at a garage sale but I’ve never messed with it. I should set it up

 

[Nutball]

This bit almost looks as if it got run at too high rpm's, yet there is no thermal discoloration.
Still, lower rpm might have caused less damage.
I like the bit, seemed to have had a good cutting edge from the factory - although the high "shoulder" right behind the leading cutting edge makes for fast dulling. This said "shoulder" is technically a dept limiter so the bit doesn't corkscrew itself into the medium being drilled - I personally regrind brand new drill bits and make them more aggressive.

This is "my normal" free hand grind which works wonders on 90% of what I drill at home.

View attachment 358483 View attachment 358484 View attachment 358485 View attachment 358486 View attachment 358487

I had a bit that was way too aggressive in aluminum. It would just about suck the drill press down.

 

[Nutball]

And this is "my special" grind - same drill bit and grind as pictured above, but with the cutters corner ground to another cutting surface.
It is basically a "semi-chisel drill bit cutting edge" and it is a thing that I picked up from industrial grade WiDia Solid-Carbide drill bits I had the pleasure to test.
This grind helps reduce the probability of the outer cutting edge from melting/chipping/wearing/dulling as fast as a regular ground drill bit would.
Again, it is a matter of what You use Your drill bit for so You don't need this mod all the time even though it doesn't hurt cutting performance at all.

This grind is excellent for processing hard steel and thin materials as there is no sharp cutter corner to get damaged or catch too big a bite while punching through the medium being processed.

View attachment 358488 View attachment 358489 View attachment 358490

Just what I need. A lot of the better looking bits I've picked up seem to have overly sharp corners that I'm afraid of chipping when drilling chainsaw bars or stainless mufflers.

 

[Nutball]

1/2" Solid-Carbide crosscut tip drill bit, mild steel alloy workpiece, no cooling, no pilot holes - drill bit didn't even care, just made a hissing sound eating into that steel block.
High rpm and high feed with chip breakage - the generated heat transfers greatly into the workpiece steel chips.
Machine processed, not freehanded.

View attachment 358514 View attachment 358517

I have wondered if faster is better or not. I hear cutting metal too fast will overheat the cutter, but then they say you can cut hardened steel so fast the chips glow without risking damage to the cutters. The only problem I see there is red hot chips can stick to the cutters allowing more time for heat transfer.

Maybe make a video?

Yes. And learn better macro picture taking skills, I know it is not easy. Maybe we can teach each other something.

 

[Wilhelm]

Just to comment on the quality of my pictures.

My Sony Ericsson Elm DUMBPHONE of 12 years with a mere 5MP camera had a selective macro mode and I could take pictures as close as 1" from the object - razor sharp pictures of a blank paper sheet showing all the grooves and fiber strands of the papers surface.
Sadly my Elm died on me and I got a "smartphone" (???!!!).
That stupid thing makes crappier pictures at 20MP than my still working K750i at 2MP. And the quality of the so called smartphone camera is extremely inconsistent, it rarely auto zooms correctly and most times just focuses on anything BUT the object I am taking a picture of.

I always said that smartphones are for dumb people, now I am one of them!

 

[Wilhelm]

I had a bit that was way too aggressive in aluminum. It would just about suck the drill press down.

That's always fun!
Drilling Aluminum is like drilling wood, corkscrew effect.

I have wondered if faster is better or not. I hear cutting metal too fast will overheat the cutter, but then they say you can cut hardened steel so fast the chips glow without risking damage to the cutters. The only problem I see there is red hot chips can stick to the cutters allowing more time for heat transfer.

Yes. And learn better macro picture taking skills, I know it is not easy. Maybe we can teach each other something.

I see sparks flying every other day processing grey cast iron (technicaly merely pig iron though!), believe me when I say that not even Solid-Carbide likes sparking mediums on the long run!

Also, whether or not and how efficiently a tool transfers the friction heat into the chips depends on many factors: tools core material, coating, cutter shape angles and sharpness, the material being processed, ...
Just because a tool can endure high rpm/feed/heat without liquid cooling doesn't mean it wouldn't perform equally well but with a longer lifespan with liquid cooling.

Look at the chip pictures I posted, closely!
They all start cold and then blue as they get cut, then the chip breakage (with spindle retract) engages letting the workpiece and drill bit cool down - on the next feed cycle the chips start flowing cool and again become thermally blued as the cut progresses.
The time it takes the machine to retract from feed and return to feed again is a fraction of a second, but it is enough to allow the generated heat to both dissipate and spread keeping the drill bits tip at an acceptable work temperature.

There are many variables that influence tool life, most can be ignored or ballparked by simply adding massive liquid cooling.

In regards to that video.
The top of an anvil is surface hardened from hammering on it.
Also, a good anvil is not mild steel , far from it.
I have seen vintage anvils broken in half, mild steel doesn't do that.
The rpm may have been a bit too high for that diameter mill head - staged for the wow effect?!
The biggest I run is a TungAlloy 67mm 6 cutter head at 1155rpm max in pig iron without cooling and it tends to spark occasionally and chip/wear the cutters fast.
Quite often the manufacturers specs for their tools rpm/feed are painfully exaggerated - one must keep in mind that manufacturer tool specs are the MAX under perfect conditions!

Apologies for the lengthy post!
I am a metal worker and machinist, it is kinda my kink.

 

[Boomer2230]

A sharpening tool helps get the angles right. And makes sure both sides are even.

 

[calcutta250]

I learned to hand sharpen drill is school as well. It takes a lot of dedication and even more practice. I rarely resharpen less than 1/8”

I also despise drill doctors. I’ve never been able to get good results with them other than helping make the split point.

The crosscut /split point has a huge advantage in work hardening materials. The split point actually cuts rather than the conventional point on standard drills. Conventional points push material into the cutting lip, this is problematic for work hardening materials.

I also refer to speed and feed charts and err on the conservative side if I’m not sure of the metal composition or condition.

I have always loved WD40 for aluminum, tap magic is great and I prefer it for most everything else.


Sent from my iPhone using Tapatalk

 

[Stevetheboatguy]

Surprisingly few replies on this topic.

Either I killed the thread or no one uses drill bits.
If it's the former, my apologies!
If it's the latter I bet asking advice on sharpening a chainsaw chain would have resulted in a 100 page thread by now.

Some of us are just meant to not have nice things. The way my stuff gets abused because of lack of access or other factors...... I just buy the cheapest crap I can find and re shape or sharpen as many times as needed. Most the time anyway.

Now if I'm lucky enough to be able and use my drill press. Well then I will use some better bits I inherited from my grandpa. But for freehand stuff. Forget about it I'll stick to the cheap stuff and wear my safety glasses.



Steven