Drill bits for hard steel

eyeeatingfish

eyeeatingfish

Joined
Dec 9, 2003
Messages
4,817
I am putting a new handle on a japanese knife blade and I bought a set or Irwin black oxide bits that the guy at the store recomended. The cobalt bits were expensive and I didnt know what size I needed. So I went and started drilling, it progressed nicely till it hit the middle layer. (got a center layer ad outer softer layers). Then it just stopped. I changed to a small bit to try and do a pilot hole and nothing. Basically once it reached the center steel it stopped and wouldnt even scratch the stuff. I used some oil while I was drilling too. I returned to the store and bought a steel punch so give it a dent to start, the steel punch didnt dent the steel. They didnt have anything diamond tipped. I know that not having the super hard drill bits would mean more frequent resharpening but it should still cut some right? I looked at diamond bits for dremel tools but they said they were not for drilling.
Any help is appreciated, thankyou

PS: I also need a way to regulate my belt sander to lower speeds, having trouble finding one at the hardware store rated at 6 amps. Closest thing is a 5 amp fan switch.
 
Like Ray says carbide, and be careful it does not take much to break one I know I break them all the time...lol

Spencer
 
I have had great success with Irwin bits but I also never drill anything harder then air cooled steel and use only 25-30 RPMs.
 
an idea i have been meaning to try is this. get a steel rod 1/4" or so and slightley round the end. then chuck it in the drill press like a bit. then press it onto the spot on the steel where you want to drill. the end of the rod will get red hot and heat up the spot you want to drill. let it cool and drill with a normal bit.
 
JTknives said:
an idea i have been meaning to try is this. get a steel rod 1/4" or so and slightley round the end. then chuck it in the drill press like a bit. then press it onto the spot on the steel where you want to drill. the end of the rod will get red hot and heat up the spot you want to drill. let it cool and drill with a normal bit.
Click to expand...

I kind of lack a drill press.
So low speed is better than high speed?
 
Hengelo_77 said:
So drilling with carbide you use low speed?
Click to expand...

Yes but I really do not have any need for carbide bits. I still have two 24 piece sets but a good quality HSS bit at very low speed works great, even on Ti.

IMHO the most important feature to have on a drill press or mill/drill unit is a very slow speed setting. At 25-30 RPM you quickly develop an intuitive feel for exactly what the bit is doing (or not).

My old drill press only went down to 300 Rpm's so w/o carbide I just smoke a boat load of bits.

"Yep and when I use them I don`t use the chuck key I only nip it up by hand ,that way if it grabs a bit it will turn in the chuck not shatter.
Richard"

Good idea! I can see the advantage on smaller bits at least.
 
The "heat it up with a piece of steel rod and let it cool" idea will work fine for simple steels (spot annealing), but for air hardening steels ,like the VG-10 core on this blade, it could actually make it harder. It most likely would not soften it enough to use a regular drill bit, in any case. Either use a carbide bit in a drill press (a hand drill will surely break a carbide bit), or use abrasive drilling. To abrasively drill a hole, make a dam of putty around the hole area. Place silicon carbide grit in the depression, add a few drops of cutting oil, and drill with a piece of flat ended steel rod. Drill SLOW and constantly raise and lower the rod. It takes time, but you can drill the hole through hardened steel this way. Coarse valve grinding compound works great for this job.
Stacy
 
In order to cut, the web has to penetrate the material. If the material you're cutting is hard, it takes a lot of pressure on the web of the bit to feed it in, otherwise it will just rub. If it is going to cut, you're going to have to lean on the bit hard. If the bit is HRC 65, and the steel is HRC 55, this might work. But that probably isn't the case...

A carbide bit designed for this will work. Most are not, they're designed for cutting abrasive material in high production such as aluminum or fiberglass. The geometry of the bit will not hold up to drilling hardened steel if it was designed for aluminum etc. If it is designed for drilling hardened material it will require a very rigid setup, possibly beyond a consumer grade drill press. Any play or chatter will ruin the cutting edge on carbide fairly quickly.

I suggest you take a rod, such as a brass rod, and some valve lapping compound like you can get at the auto store and lap through the hardened steel using your hand drill at high speed. It will take 10 or 20 min I expect.

It is counter intuitive, but the harder material wears away faster than the softer because the grit embeds in the softer material and cuts the harder.
 
What angles and etc should a carbide drill be to drill hardened steel. I have some carbides how do I sharpen them (have diamond wheel) and care for them. Drill in my mill only? Thanks Jim
 
ib2v4u said:
What angles and etc should a carbide drill be to drill hardened steel. I have some carbides how do I sharpen them (have diamond wheel) and care for them. Drill in my mill only? Thanks Jim
Click to expand...


I'm not a tooling engineer, but I'll make some observations.

The yield point for aluminum might be 20,000 PSI, soft steel 60,000 PSI, hardened steel 300,000 PSI. The cutting geometry must be very strong for hard steel.

Carbide for aluminum has deep flutes and a lot of edge relief behind the cutting edge for high chip loads for high feed rate. I've also noticed a high helix angle for the flutes, not for chip removal, but because it lends itself to a sharper cutting edge at the tip. This thin shape cutting edge hauls ass in aluminum or abrasive plastic, but will fail when subjected to hardened steel.

Carbide for steel is a different grade of carbide with more cobalt binder (trades wear resistance for toughness) shallow flutes for edge reinforcement and less edge relief, also for edge reinforcement. They often have shallow helix or even a straight flute.

A lot of carbide drills are for circuit boards and will not work well in hard steel.

To sum up, cutting edges for aluminum are ground deep and sharp, cutting edges for hard steel are ground shallow and strong...
 
Just to add to Nathan's advice, Never use carbide on annealed or mild steel, it's to gummy and will break the carbide right off, also you can get Diamond Dust Drills for about $20.00 a pop at your local Lowes Hardware Store might be a less expensive route in the long run.

754005280201.jpg
 
I haven't tried it but Wayne Goddard claims to use a concrete bit to drill hardened steel.
Lynn
 
J.S. Carter said:
Just to add to Nathan's advice, Never use carbide on annealed or mild steel, it's to gummy and will break the carbide right off,
Click to expand...

That's news to me.

Gummy aluminum (full soft) and pure copper (110 etc) are so gummy they cause problems, but I haven't ever heard of gummy steel causing problems. Chunky steel, like with bits of a bumper off a '73 Buick still showing in it, can be bad...

The steel they sell in hardware stores is some of the lousiest crap...
 
Lynn said:
I haven't tried it but Wayne Goddard claims to use a concrete bit to drill hardened steel.
Lynn
Click to expand...

Yeah, that makes sense. A spade bit would be the ticket, and that is basically what in on the tip of a concrete bit. Might help to put a better edge on it on a green stone or something first.

I'll bet that works. Never tried though...
 
I tried it with out much success. It may be more effective if you do as Nathan suggested and reworked the carbide. The edges are pretty blunt I believe to take the shock of the hammering in a masonry drill.
 
You must log in or register to reply here.
Back
Top