drilling holes in hardened material

BossDog

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
The first rule of drilling holes in hardened material is to avoid drilling in hardened material. Seriously.

Plan your work ahead of time. Always drill before hardening.

There are basically three types of metals used for drilling. HSS, Cobalt based, Carbide based.
HSS works well for wood and mild metals. Cheap.

Cobalt works well for nearly everything else - except hardened steel or other very hard metals. More expensive but probably best value for length of life cycle.

Carbide is used for drilling hardened metals of other materials that dull Cobalt or HSS too fast. Carbon fiber comes to mind.

Find a drilling chart that shows RPM's vs diameter vs material. Use that as a guide to set up your drill press speeds. When drilling with carbide, double the speed (RPMs) suggested for HSS.

Use cutting/drilling lube when drilling - always. It will greatly improve the life of your drill bits and give you cleaner, rounder holes.

Carbide drills will not tolerate bending like HSS or Cobalt drills. Using the same hand holding technique for carbide drills will get you broken or prematurely failed drills. Clamp your work down when using carbide or buy extra drills when you break them. Avoid using carbide drills in a hand drill or you will have a great collection of expensive broken carbide drills.

There are different styles of drill bits, ie: spade, straight flute, carbide tipped, helical, etc. Use the right style for the job. Just because it is carbide or carbide tipped doesn't mean it is going to work well, or at all.

Carbide drills or tools are commonly used in CNC applications where the feeds and speeds are precisely calculated and applied. Hand drilling hardened materials with a drill press requires attention to technique by always clamping, RPMs and pressure applied. Applying light pressure to "save wear" on a drill bit is probably the best way to dull a drill bit.

Something to keep in mind. CNC machining defines how tools are made and used today. Knife makers generally use drill presses and hand made craftsmanship. These are often two different things.
 
Yes sir, learned this the hard way. Didn't think I was ever going to get the pin hole drilled through on the pin closest to the ricasso.
 
Thanks for the excellent post!

"Applying light pressure to save wear on a drill bit is probably the best way to dull a drill bit". I didn't know this early on, but believe it to be true just by personal experience. Good pointer, right there!
Also, I have found that a "Carbide-tipped masonry bit" can cut a hole in hardened steel, if you need a carbide tipped bit in a pinch. No cutting fluid, high speed, and pressure, and it will go thru a hardened tang (I've done it once). It's like nails on a chalkboard tho. I have not tried that particular "carbide tipped masonry bit" technique with proper RPM, pressure, and cutting fluid, so can't speak to that. And the hole will be slightly oversized. But....something to file away in the ol' memory banks.
 
Great thread, I'll add that everyone should have a drill doctor on their Christmas list this year. I think it's the 500 model I have and it's really nice to bring a bit back too like new in seconds verses using a dull bit and just getting frustrated. they won't work for real small bits so I only buy cobalt in small bits, but that drill doctor has saved me a fortune.
 
I was working on a trailer at my home I welded up a bunch of old bed iron. Now one would thing the angle iron off of a bed would not be the best of stuff. However when I got the trailer all welded up and started drilling holes to fasten the boards I found out I could not drill those pieces of angle iron. After burning up 3 bits I went to an old friend. He had been a machinist all of his life. I explained what was going on and I was gonna go broke buying bits to finish this trailer. He asked me the size and when I told him he says come with me.

We went out to his shop on the property and he fished around and came up with an old masonry bit! I am thinking oh crap, the old man has gotten senile! He takes the bit over to the round wheel grinder he has in the shop. He grinds on the bit a minute all by eye. When done he turns around and hands me the bit. He explained he had to put a cutting edge on the carbide because when drilling concrete you do not need a sharp edge and I changed the angle to 135* as that will cut metal better. He also told me when drilling with this bit put all the pressure on it you can and run it as fast as you can!! I looked at the bit and I could see right away that his eye had put as pretty point on the bit as I ever seen. I asked him how he learned to do that by eye so easy. Practice Son, practice!! He said when he first started the guy that owned the shop told him here, and handed him a box of dull bits. They ranged in small to huge sizes. I sharped all morning and took the box over to him right before lunch. He picked a couple of bits out of the box, looked at the rest. He handed me the box back tossing the two he had in his hand and said. After lunch you can sharpen them so they will actually cut. He looked at me and said, practice Son, practice!!


I took the masonry bit home and thinking all the time this isn't going to work. I drilled about 40 holes with that bit and it cut well, down to the last four or five. It had lost its sharpness and it took all I could do to make it cut!! The next chance I got to see that ole man again he was down with Cancer. He told me that they it was terminal but that they could do Chemo and maybe I would get a few months more. I told them what for I am ready to meet my maker, and a month later he was gone.

I have always wished I had meant him earlier in life. That old man new his stuff when it came to machine work. Watched him run a cutting torch making a 5' cut on a chalk line and never wavered more than an 1/8". We were all remarking at how straight the cut was and without a straight edge. He looked at us and said, in my younger days it would have even been straighter! I miss that old man!!
 
bladegrinder said:
Great thread, I'll add that everyone should have a drill doctor on their Christmas list this year. I think it's the 500 model I have and it's really nice to bring a bit back too like new in seconds verses using a dull bit and just getting frustrated. they won't work for real small bits so I only buy cobalt in small bits, but that drill doctor has saved me a fortune.
Click to expand...

I second that. Best money you can spend in the long run. I have the old version and it's still running strong.
 
C Craft said:
I was working on a trailer at my home I welded up a bunch of old bed iron. Now one would thing the angle iron off of a bed would not be the best of stuff. However when I got the trailer all welded up and started drilling holes to fasten the boards I found out I could not drill those pieces of angle iron. After burning up 3 bits I went to an old friend. He had been a machinist all of his life. I explained what was going on and I was gonna go broke buying bits to finish this trailer. He asked me the size and when I told him he says come with me.

We went out to his shop on the property and he fished around and came up with an old masonry bit! I am thinking oh crap, the old man has gotten senile! He takes the bit over to the round wheel grinder he has in the shop. He grinds on the bit a minute all by eye. When done he turns around and hands me the bit. He explained he had to put a cutting edge on the carbide because when drilling concrete you do not need a sharp edge and I changed the angle to 135* as that will cut metal better. He also told me when drilling with this bit put all the pressure on it you can and run it as fast as you can!! I looked at the bit and I could see right away that his eye had put as pretty point on the bit as I ever seen. I asked him how he learned to do that by eye so easy. Practice Son, practice!! He said when he first started the guy that owned the shop told him here, and handed him a box of dull bits. They ranged in small to huge sizes. I sharped all morning and took the box over to him right before lunch. He picked a couple of bits out of the box, looked at the rest. He handed me the box back tossing the two he had in his hand and said. After lunch you can sharpen them so they will actually cut. He looked at me and said, practice Son, practice!!


I took the masonry bit home and thinking all the time this isn't going to work. I drilled about 40 holes with that bit and it cut well, down to the last four or five. It had lost its sharpness and it took all I could do to make it cut!! The next chance I got to see that ole man again he was down with Cancer. He told me that they it was terminal but that they could do Chemo and maybe I would get a few months more. I told them what for I am ready to meet my maker, and a month later he was gone.

I have always wished I had meant him earlier in life. That old man new his stuff when it came to machine work. Watched him run a cutting torch making a 5' cut on a chalk line and never wavered more than an 1/8". We were all remarking at how straight the cut was and without a straight edge. He looked at us and said, in my younger days it would have even been straighter! I miss that old man!!
Click to expand...


Those old guys are rare gems these days! I've met many an older man in factories and shops around the country who were outright wizards when it came to solving problems with the most basic of equipment and years and years of experience. You can spot a man instantly who has been there and done that and gotten the t-shirt.
 
I've got the 750X Drill Doctor, and it does work ok. Each time I use it I have to relearn how it's done. I normally just freehand sharpening a drill bit in. Heck, if you can freehand grind a blade, sharpen a blade, you CAN learn to freehand sharpen a drill bit..... above 1/4" or so anyway.
 
I used to be very good at sharpening drills by hand, when I did it all the time. However, there were plenty of times that I ended up "fixing" what I'd done several times and my drills looked like that pencil you had in your desk in 5th grade that was about equal parts wood and metal eraser ferrule. The drill doctor is as easy as it gets. zip zip zip. done. They are a little pricey, but you can find them on ebay, etc. I bought mine used from a mechanic in the plant where I was. It was old then, and it was 15 years ago when I bought it. Mine's probably the first model you bought at 3am off TV. The new one does split points, mine doesn't.
 
you can use your drill to make a guide if you can't get the set up on the drill press. Drill a piece of scrap metal 1/2 to 3/4 thick with your drill on the drill press. Then clamp it to your knife,etc. with the hole over where you want to drill. It'll keep you nice and straight.

Don't split the point on a carbide drill. It will usually break coming through the other side. You can thin the web a bit for less pressure as that will not make it weak in the center.

Learning to hand sharpen drills is very similar to learning grind blades....only cheaper and easier.lol. Definitely worth the practice, though. Oh, and, on smaller drills, use a somewhat fine wheel. And keep it dressed(FLAT!). You can buy surface grinder wheels that cut smooth and are of much higher quality that the wheels that come with your grinder. Do your coarse grinding on your rough wheel and the pretty stuff on fine wheel. Dunk in water often.

I still do all my grinding by hand(carbide too...I have diamond wheels)...have for 30 sumpin' years. I do have to use specs now cause my eyes are goin'. I sharpen friends drills for free to stay in tune. You will make friends doing this and it doesn't take much of your time.

Nice thread
 
Here's a good cheap tool to learn sharpening with. You can also make a simple version of this on a belt grinder.

http://www.acehardware.com/product/...Ayf2dAbl-hcBp22Kff6ewJG2tb1ezsgBoCXmQQAvD_BwE

For discussions sake:
Twist_Drill_-_Point_Feometry.png

If you grind the flute where it meets the lip flat and parallel to the length of the drill,(just a little bit...1/16 or so) it will make it much stronger for the "break through". It will take more pressure to drill and will make powdery chips and a "scritching" sound as it drills. This is done often for cutting thin brass which is "grabby" or any thin sheet metal. I have used this on hard materials with pretty good success. I usually thin the web a bit when doing this.

Hope this helps....
 
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"The first rule of drilling holes in hardened material is to avoid drilling in hardened material. Seriously."....Tracy Mickley

This is probably the best advise given on this thread...Lol. Take it to heart...

 
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