what type of drill bit to drill harden steel

Rkh · Sep 4, 2014

I have a 3/4" hardened steel trying to put 1/8" hole but keep breaking bits. What type bit do I need?

Mike M · Sep 4, 2014

Carbide. Try a carbide masonry drill. Cheap and sometimes they will work.

Bill in IL · Sep 4, 2014

Cobalt drills of good quality with lots of cutting oil. Hopefully you can use a dril press as well.

TimV · Sep 4, 2014

Either good cobalt or carbide drills will do it, but one thing to be careful of--deep drilling like you're trying to do will require VERY frequent removal of the drill from the hole in order to clear the chips. Otherwise, you're going to break bits, even more so as cobalt and carbide are both quite brittle, and getting a broken bit made from either one out of a hole is going to be quite a project.

bison · Sep 4, 2014

(quoted from post at 10:22:36 09/04/14) Either good cobalt or carbide drills will do it, but one thing to be careful of--deep drilling like you're trying to do will require VERY frequent removal of the drill from the hole in order to clear the chips. Otherwise, you're going to break bits, even more so as cobalt and carbide are both quite brittle, and getting a broken bit made from either one out of a hole is going to be quite a project.

his ^^^ and
Heat is your enemy,use lots of coolant and stop start the drill press taking it a few slow bites at the time often works
If you work harden the steel by using a dull bit then drilling becomes near impossible.

Wile E · Sep 4, 2014

Get a carbide or Cobalt drill, run the drill real slow, under 200 rpms. If you can get a mapp gas torch and heat the metal up till it is blue.....let it cool real slow.....Then start drilling.

Heating it up till it is blue will take some of the hardness out of it.

Dick L · Sep 4, 2014

A lot depends on how hard (hardened) is. 1/8" is a small drill and will not take much down pressure. Some real hard steel would need EDM'ed or annealed, drilled and re hardened.

black · Sep 4, 2014

Try asking for a drill bitt that will drill stainless steel and it could be cobalt or carbide (not sure ). I drilled some stainless counters and had success with the bit, so it should also drill your 3/4 " hardened steel.

Larry -- Ont.

Samtn1 · Sep 4, 2014

Agree. Without knowing how hard it is, it is impossible to know what to use. In any case, drilling a 1/8 hole that deep into hardened steel will be a challenge. You can try a concrete bit like someone suggested. If that doesn't work, take it to a machine shop that has an EDM.

Steve@Advance · Sep 4, 2014

If you're trying to hand drill it a carbide tip masonry drill will be your best bet. Solid carbide will not work with a hand drill!

Using a drill press or mill would be much better.

With a HSS drill run about 1000 RPM, lots of oil/coolant, peck the hole to clear the chips and allow it to cool.

With a carbide run about 2000 RPM, light pressure, no sudden moves!

KirbyandLugnut · Sep 4, 2014

A sharp one

HenryO · Sep 4, 2014

The only answer is Cobalt bits. They are good for stainless steel also.

ss55 · Sep 5, 2014

Do you know the Rockwell hardness of the steel?

what type of drill bit to drill harden steel

Rkh

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Bill in IL

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TimV

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bison

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Wile E

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black

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