What are the strongest drill bits for steel?

[audiophil2]

I have Dewalt cobalt bits and they are wearing out fast. I run at 360-400rpm and have a bit sharpener. Is there something stronger?
1/8-1/4" sizes.

[liber]

Carbide!

Wait, I should re-preface that. If you want long lasting cutting ability, carbide would be a good choice.

Could you define "strongest" ?

[Ninety]

There is a tool company that is at all of these shows I attend.. they do some pretty crazy stuff with their bits..

here they are

https://baddogtools.com/

ETA id idn't realize the forum.. may not be the right thing for machining.. I agree with above^

[wilit]

I have some magazines that I needed to drill for some floorplate extensions. Cobalt bits wouldn't even make a dimple in the hardened plates. Carbide bits ($$$) were the only thing that would drill it.

[kendog4570]

They don't have to be strong, they just have to be good. Stay away from hardware store homeowner junk and get Cleveland or Chicago Latrobe. They are good for jobber length drills. Hertel are OK for import. I am sure there are many other brands of good bits. Rule of thumb is avoid the crap at Harbor Freight or Ace or Home Depot or Orchard Supply or...???. Try to stick with 135 deg drill points, they work better for most gun related applications.
You have to be good too. Feeds and speeds, and paying attention to what the bit is telling you when you use it. The last comes from experience. If you are not going deep, use screw machine drill bits. Much more rigid than jobber length. Start your holes with center drills.

[TexasJackKin]

They don't have to be strong, they just have to be good. Stay away from hardware store homeowner junk and get Cleveland or Chicago Latrobe. They are good for jobber length drills. Hertel are OK for import. I am sure there are many other brands of good bits. Rule of thumb is avoid the crap at Harbor Freight or Ace or Home Depot or Orchard Supply or...???. Try to stick with 135 deg drill points, they work better for most gun related applications.
You have to be good too. Feeds and speeds, and paying attention to what the bit is telling you when you use it. The last comes from experience. If you are not going deep, use screw machine drill bits. Much more rigid than jobber length. Start your holes with center drills.

^^^^This!^^^^
Only consider carbide if you have a completely ridgid set up. Think milling machine and collets or a very good quality chuck like an Albreht.

[Dnele928]

...and apply cutting oil liberally...one circumstance where liberally is a good thing...

[kcstott]

in steel a 1/8" drill bit should be spinning at 2880 Yeah most drill presses and mills will not go that fast so as close to 2000 as you can get

1400 RPM for a 1/4"

Hardened steel cut those speeds in half at least
Aluminum double them.

['ol shooter]

Hi Roc Cobalt bits are pretty tough.

[Ryan in SD]

Carbide may or may not be good. It depends on what and how you are drilling.

Carbide is very susceptible to chipping and doesnt hold up with pecking in steel so much unless you retard the feed rate on entry. Dont be suprised if you break the corners off the cutting edge.
The problem is, it wants to grab and twist but carbide doesnt want to twist. It will cut amazing at first, but I think in hand drill applications the life probably wont be very long in hard steels.

HSS or cobalt should be around 60 SFM

Carbide can be 100-200 SFM or so.

rpm should be (12 X sfm) / (drill dia. X 3.14)

Always better to start conservative and get a feel for it before ramping up speed and feeds.

Also use cutting fluid and as stated. Stay away from junk tools. Get something from MSC or a reputable tool maker.

Ticn coated will be more forgiving for hand applications but a bit more expensive.

[shafferds]

Zrn coated is better for aluminum than ticn.

[Victor Cachat]

I bought one Dewalt Cobalt bit and it chipped the first time I used it.
Since then, I replaced my everyday drill index with 135 degree Cobalt bits from Enco.

You can buy sets too: http://www.use-enco.com/1/1/54120-he...-337-2807.html

[kcstott]

Carbide may or may not be good. It depends on what and how you are drilling.

Carbide is very susceptible to chipping and doesnt hold up with pecking in steel so much unless you retard the feed rate on entry. Dont be suprised if you break the corners off the cutting edge.
The problem is, it wants to grab and twist but carbide doesnt want to twist. It will cut amazing at first, but I think in hand drill applications the life probably wont be very long in hard steels.

HSS or cobalt should be around 60 SFM

Carbide can be 100-200 SFM or so.

rpm should be (12 X sfm) / (drill dia. X 3.14)

Always better to start conservative and get a feel for it before ramping up speed and feeds.

Also use cutting fluid and as stated. Stay away from junk tools. Get something from MSC or a reputable tool maker.

Ticn coated will be more forgiving for hand applications but a bit more expensive.

I disagree on the Tinc being more forgiving on hand drilling.

Tin, Tian, coating were designed for production machining, they reduce heat build up in the tool which will increase wear and decrease tool life.

You will not see a difference in a drill press or hand drill application unless you are making more then 100 parts.

Although it will help in one drill press or hand drill application that I can think of and that is Titanium.

Now that said Carbide should never be used in a drill press period.

Your long drawn out formula while correct a lot of people don't have the motivation to google a damn thing you think they are actually going to try and plug this into a calculator??

A simple formula for steel is 360 / cutter diameter for a mill or part diameter on a lathe, the true formula is 343 / cutter diameter @ 90 SFM but we all know the speeds and feeds are suggested starting points.

so a 1" cutter is 360 RPM
1/2" = 720 RPM
1/4" = 1440
and so on

Once you have this base in your head just double it for carbide and half it for harder materials

99% of mill work is done between 600 and 1400 RPM on a conventional machine


BTW Mcmaster carr is a better source for drill bit and endmills then Enco MSC will ever be, For those that don't know MSC has owned Enco for decades and they recently bought out Rutland tool as well, Rutland was the only decent independent tool supply house in southern California. MSC and enco are over priced for what you get. Mcmaster supplies Cleveland and latrobe along with Hanson and greenfield for taps. and they are priced very well and arrive the same day or next day

[Reloaderdave]

I disagree on the Tinc being more forgiving on hand drilling.

Tin, Tian, coating were designed for production machining, they reduce heat build up in the tool which will increase wear and decrease tool life.

You will not see a difference in a drill press or hand drill application unless you are making more then 100 parts.

Although it will help in one drill press or hand drill application that I can think of and that is Titanium.

Now that said Carbide should never be used in a drill press period.

Your long drawn out formula while correct a lot of people don't have the motivation to google a damn thing you think they are actually going to try and plug this into a calculator??

A simple formula for steel is 360 / cutter diameter for a mill or part diameter on a lathe, the true formula is 343 / cutter diameter @ 90 SFM but we all know the speeds and feeds are suggested starting points.

so a 1" cutter is 360 RPM
1/2" = 720 RPM
1/4" = 1440
and so on

Once you have this base in your head just double it for carbide and half it for harder materials

99% of mill work is done between 600 and 1400 RPM on a conventional machine


BTW Mcmaster carr is a better source for drill bit and endmills then Enco MSC will ever be, For those that don't know MSC has owned Enco for decades and they recently bought out Rutland tool as well, Rutland was the only decent independent tool supply house in southern California. MSC and enco are over priced for what you get. Mcmaster supplies Cleveland and latrobe along with Hanson and greenfield for taps. and they are priced very well and arrive the same day or next day

^^^THIS^^^
I agree 100%, especially about using carbide in a drill press. Don't even try, a drill press is not rigid enough for carbide cutters and the chuck will not run true enough either. If you resharpen cobalt drill bits, you will need to learn how to thin the web after sharpening because cobalt drills are made with a thicker web than high speed drills, or learn how to put the chisel point back on. That's a learning curve that takes practice. RL Stevens also is a good source for cutters as well as McMaster Carr.

[glockman19]

Call Mike at www.drillbitwarehoue.com He'll help you chose the proper drill bit for your application.