What are the best drill bits for hardest steel?

[johnlarson]

Drilling into metal is a lot harder than drilling through wood, and then need a tougher drill bit. Suggest me which are the best drill bit for steel?

 

[Phil Dart]

Drill bits with added cobalt are generally used for drilling steel I think. A quick google for cobalt drill bits will bring up a good few places to buy them in your country I suspect.

 

[21William]

You can get solid carbide Drill bits for drilling tough steels but they can be expensive.

I’ve used glass drills for (delicately) opening up existing holes in hard steels.

 

[Dalboy]

As Phil stated cobalt drill bits. But all you say is hardest steel and don't mention specifically which type of steel.

 

[Penpal]

Open ended request Larson but not a big one,easily solved in California. With the detail info of your challenge Mr Google could be your best friend supported by manufacturing businesses. The drill pictured will drill through files and glass etc I used them to drill solidified rock in Macedon tooth.

Peter.

 

[wm460]

I mostly use High-Speed Steel (HSS), Cobalt (HSCO) drilling into hardened steel and stainless steel.

 

[Bill Mooney]

Titanium nitride coated bits or cobalt as Phil says.

 

[EStreet]

The only good way to drill hardened steel is solid carbide bits. Carbide flute bit that’s small then ream with a solid carbide spade bit. Don’t waste your time with TiN or cobalt bits on tempered steel.

 

[johnlarson]

I'm trying to think out which type of bit is best for drilling thru about 1/4" of galvanized steel. I recently used a standard carbon-steel bit to drill thru the steel. While the bit was able to drill thru it once, the second time barely made it because the bit was dulled by the first hole.

 

[EStreet]

You want something harder than what you are drilling. That way it cuts the material and not dulls the bit. Bits will dull with use and heat. Heat being the #1 enemy so you need cutting fluid.

1/4 steel you should get a carbide flute bit.

 

[Walter]

If it is galvanised then it is likely to be mild steel and an ordinary jobber bit should go through it without a problem if you use the correct speed and pressure and some cutting fluid. As Ed said, heat is the biggest enemy.

 

[EStreet]

Galvanized means it has a layer of zinc on it. Also FYI zinc vapor WILL not can but WILL kill you.

 

[johnlarson]

I was drilling deep holes in soft materials, but the flutes will get packed with chaff, and it will stop cutting. I don't understand whats wrong with my tools

 

[Walter]

I was drilling deep holes in soft materials, but the flutes will get packed with chaff, and it will stop cutting. I don't understand whats wrong with my tools?

If the flutes are getting filled with swarf it is your technique that is at fault not the tools. You need to withdraw the bit regularly to clear the swarf.

 

[Dalboy]

Some metals when worked will produce long pieces of swarf where as others will chip more readily. If you are getting long pieces then as Walter stated you need to take the pressure of which will break the long chips this will need to be done regularly so that the chips can clear.

 

[21William]

The most common problem when drilling steel is that people run the drill bit too fast and don’t use a suitable cutting fluid.