Recommended drill bits for hardened steel?

[Skeletor]

Boron steel bits work pretty good and are easy to get. I use them when drilling hardened steel at work. As stated go slow. If your an animal you’ll work harden it and your done.

 

[rScotty]

This is excellent! Thank you for taking the time to educate me, and probably, others on here!!! A+++

Eric wrote: "So, to sum things up, use cobalt split point stub length drills, low RPM, high pressure, and cutting oil. And back off the pressure as the drill breaks through."

To that excellent advice I would add to start with a center punch, drill a pilot hole, and step up in reasonable increments.

And don't forget that the drill chuck is important too. There is a lot of variation in the quality of drill chucks, and the mounting system is fairly standard. Chances are good that an upgraded chucks is available in a taper and thread to fit your drill.
Now that you are getting some good drill bits, might as well put some thought into holding them so they don't slip....much.....
rScotty

 

[sandman2234]

my one last piece of advice is to use a quality cutting/ tapping fluid, tap magic is a reputable brand that you can usually find locally. It makes a big difference especially in hard to machine materials. Dont use engine oil, or WD40, or grease, or soap or anything else besides cutting oil.

I just wanted to mention that WD-40 makes a very good lube when machining aluminum! It keeps the aluminum from sticking and leaves a pretty good finish on a part if you are milling a piece. Otherwise, I never use WD-40...
David from jax

 

[jaxs]

You've received good information but imo no one made strong enough case for using a drill press. I'm able to drill far more holes with a press between sharpening and through material I can't drill with hand held drill. If you've never owned a press even a $40 used bench model will make a world of difference. I'm no good at sharpening bits freehand so I have an electric sharpener with jig. I have some expensive bits I rarely need,99% of holes are with HSS bits that have been sharpened and re-sharpened. Even HSS in large sizes are really expensive so I watch for boxes of misc bits at estate sales and auction. What you save buying a box of used bits for $3 will go a long way in buying a sharpening machine.

I have simple holders with double rows by size. If I dull a bit before finishing I put dull bit in a rack with others to be sharpened then take it's twin from sharp bit holder.

Experts will probably frown on this but I've done it several times without regret. To put a hole through hardened steel without a special bit I torch heat the spot past cherry until it gos to orange/yellow. For a small piece I bury it in a bucket of sand which I had buried a piece of hot metal earlier. For a large piece I clamp Kaowool or ceramic blanket on front and back then throw a welding blanket over it. Allow part to cool until it can be handled with bare hands. Needless to say,material surounding hole will no longer be hard as before unless going through hardening process before puting part to use. I usually opt for the expensive bit if hardness near hole is critical.

Easier but uglier than above. Torch cut oversize hole then weld mild steel patch(es) with drilled hole or washer over torched hole. Did I mention how sloppy my torch cuts are?

 

[Sawyer Rob]

For aluminum, I usually use Pam (the cooking spray) it works very good.

SR

 

[shock]

To follow-up, I ordered some Cobalt m42 drills, a Drill doctor sharpener, and 2 cans of cutting oil.

I appreciate all the input provided - very very much!

Oh, and I already have a drill press !

Any thoughts on use of step drill bits? Obviously not what I'd consider precision holes, at least not in my hands, but can make larger sized holes when needed and large drill bits are expensive when you don't use them 1x a year.... Thoughts?

 

[ArlyA]

Eric wrote: "So, to sum things up, use cobalt split point stub length drills, low RPM, high pressure, and cutting oil. And back off the pressure as the drill breaks through."

To that excellent advice I would add to start with a center punch, drill a pilot hole, and step up in reasonable increments.

And don't forget that the drill chuck is important too. There is a lot of variation in the quality of drill chucks, and the mounting system is fairly standard. Chances are good that an upgraded chucks is available in a taper and thread to fit your drill.
Now that you are getting some good drill bits, might as well put some thought into holding them so they don't slip....much.....
rScotty

Any hole over 3/8 that's I'm drilling, I pre-drill a small pilot hole. I thought everyone did? All with cutting oil.

 

[the old grind]

Any thoughts on use of step drill bits?

Stepped bits are for sheet metal to make round vs oddly shaped holes. One can fake it for slightly thicker metal than the distance between steps. As with any drill bit they have a cylindrical margin and wobbling will do more to dull the tool than to improve the hole in any way.

btw, glad to see other toolmakers check in. Oh, and with a trickle going on plain water is a vastly underrated coolant when out in the yard. IMO so is ATF in moderation elsewhere. Carbide is better left to use in mills than DPs and will typically crumble if used in a hand drill. This has all been covered above and was a good read till I showed up.

 

[kozal01]

Stepped bits are for sheet metal to make round vs oddly shaped holes. One can fake it for slightly thicker metal than the distance between steps. As with any drill bit they have a cylindrical margin and wobbling will do more to dull the tool than to improve the hole in any way.

btw, glad to see other toolmakers check in. Oh, and with a trickle going on plain water is a vastly underrated coolant when out in the yard. IMO so is ATF in moderation elsewhere. Carbide is better left to use in mills than DPs and will typically crumble if used in a hand drill. This has all been covered above and was a good read till I showed up.

Water soluble coolant like used in CNC machining centers works great from a spray bottle on drills in the press or hand drill and I prefer it over oil, its just harder to come by for most people.

 

[Rustyiron]

I don't know you or exactly what you're drilling, so don't take this as an insult or attack. I worked construction and fabrication and know lots of people who needed some coaching when using drills. Number one issue was mashing the trigger all the way. Others were not enough pressure and no lube. Some could go through 10 X as many bits as others.

There are all sorts of bits with regard to the material they're made of, grinds, etc. More information would help someone more knowledgeable than I give you some great input.

Very "gently" put!