Help!!! Drill bit stopped cutting

Diego_B

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Alright so sorry to any machinists I may disappoint here with my ignorance. Anyhow today I was working on two knives I have for some customers and on the blade portion there is a 7/8 in diameter finger hole. My problem is I was drilling the hole with a typical (Milwaukee) step drill bit that is new and when I got to 5/8in hole the bit just stopped cutting. Like when I mean it stopped the bit does not go a millimeter more further. I’ve tried all I know at the time to resolve the issue. So far I’ve attempted to anneal it, change drill press RPMs, and yes I am using lubricant to keep the heat down. This is a stock removal project so it should be soft. The steel is from New Jersey Steel Baron and I know it’s good stuff but it’s giving me a hell of a time. I thought about buying a carbide tipped masonry but because the seems to help a few people. But right now I’m pretty stuck, anyone have any ideas? I would be more than happy to take any advice I can get.
 

Keith Nix

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Jan 3, 2018
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Drills get dull, particularly cheap drills. You've work hardened your steel now. If there's a machine shop close by they could do a circular interpolation on a CNC mill, you could grind past the work hardened part with a dremel or foredom, or get a 7/8 carbide drill, which will probably make a godawful mess in a drill press.
 
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J. Hoffman

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When I first started making knives I had the same issue trying to drill a hole. Brand new bit got half way to through cutting like butter and then just stopped cutting....stopped dead. I tried, a new bit and cutting fluid with still not success. After trying for a half hour I discovered my quill had simply run out of travel. I raised the table a turn and the bit finished the job. Lesson learned, don't overlook the simple stuff.
 

Lorien

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When I first started making knives I had the same issue trying to drill a hole. Brand new bit got half way to through cutting like butter and then just stopped cutting....stopped dead. I tried, a new bit and cutting fluid with still not success. After trying for a half hour I discovered my quill had simply run out of travel. I raised the table a turn and the bit finished the job. Lesson learned, don't overlook the simple stuff.
I can relate haha
 

A.McPherson

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For future reference, there are piloted carbide hole saws available in individual sizes that come in very handy for finger holes.
I wish I had known that when I made this karambit!! It would have saved me a lot of headache!!

tmb3w7q.jpg
 

Drew Riley

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Even a standard bi-metal hole saw will work pretty well if you keep the speed down and use a good cutting oil. You'll want to clean things up after, but you'll likely have to anything, regardless of the method used.
 

weo

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If you haven't already, I'll suggest getting some resources on cutting speed for various drill bit sizes and materials. In the most recent Hot Iron News (the quarterly newsletter of the NWBA) there was an article by a machinist called "Drilling Holes: A Few Pointers form a Machinist" and here's some info that might be useful:

- "When drilling a small hole, the initial tendency is to have your RPM too slow. This often results in the drill bit breaking, because the pressure being applied (the “feed rate”) at low speed results in too much “chip load,” meaning it’s trying to cut too much in one revolution.
- Here is the simplest formula to come up with an RPM that will work with a wide variety of low-carbon steels: 240/drill bit dia = RPM
- What do you do when using a hand drill and you don’t know what RPM you are running? Start with guessing. We all can tell if the drill is running at its full speed or barely turning. For small drills, pay attention to your chip. If you start seeing your chip get very thick, you need more RPM and less pressure. For larger drills, if your chips are blue you are starting to run too fast.
- When drilling larger holes, a common practice is to drill a small hole in your material, and then work your way up. The reasoning is that it takes less force or pressure to move the drill through the material. The problem is that the drill bit tends to grab, which can break the bit . . .try using a pilot hole just a bit larger than the chisel point on your final drill bit, and drill the hole in two steps.
- a drill bit with a split point will take less pressure than a drill bit with a chisel point.
- Some drill bits have a gold coating and it’s probably a very good choice. This gold coating is harder and more slippery and works better than the substrate that the drill is made of. That doesn’t mean you can’t sharpen one of these drills - you just lose the benefit of the coating.
- another common option you may have at the hardware store will be a cobalt drill bit and this is usually the best drill bit you can find there for drilling steels.
- Cobalt increases what is called “red hardness.” and the higher the % Cobalt, the better the bit holds up to heat.
- When drilling stainless steel, at least 5% cobalt holds up well and you’ll need to slow your cutting speed
- For stainless, you need a sharp drill bit (Will the cutting edge of the drill scratch your fingernail? If not, it’s not sharp enough for stainless
- You do not want your drill bit to rub. This can cause “work hardening.” To keep your drill bit from rubbing you need a little higher feed rate or more pressure. If you’re not making a chip you’re rubbing.
- use oil, or coolant with a higher percent of cutting fluid, not water. Stainless needs the lubrication."

here's some of what he had to say about stainless:

- When drilling stainless steel, I have found at least 5% cobalt holds up well.
- Stainless is tougher than low carbon steel but it is not necessarily “harder” so it’s more like drilling rubber than glass.
- For stainless, you need a sharp drill bit (Will the cutting edge of the drill scratch your fingernail? If not, it’s not sharp enough for stainless).
- You’ll need to slow your cutting speed down to somewhere close to 35 to calculate your RPM. (what this means is that the equation above changes to 210/drill bit dia= RPM)
- You do not want your drill bit to rub. This can cause “work hardening.” To keep your drill bit from rubbing you need a little higher feed rate or more pressure.
- use oil, or coolant with a higher percent of cutting fluid, not water. Stainless needs the lubrication.
- You need bit with increased web thickness if you are being aggressive and drilling through a tough material like stainless.
 

Diego_B

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For future reference, there are piloted carbide hole saws available in individual sizes that come in very handy for finger holes.
Just discovered those today as well from another thread. Wish I would of known that before hand.
 

Diego_B

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I also thought of going with a cobalt step bit in order to finish the job, would this cut it if it’s work hardened? Or what about masonry bits? I’m pretty much willing to buy any bit right (as long it ain’t stupid expensive) now that will just get the darn hole drilled.
 

Diego_B

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When I first started making knives I had the same issue trying to drill a hole. Brand new bit got half way to through cutting like butter and then just stopped cutting....stopped dead. I tried, a new bit and cutting fluid with still not success. After trying for a half hour I discovered my quill had simply run out of travel. I raised the table a turn and the bit finished the job. Lesson learned, don't overlook the simple stuff.
I did that once and after figuring out what the problem was I just called it a day.
 
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For future reference, there are piloted carbide hole saws available in individual sizes that come in very handy for finger holes.
Oh my gosh!!! I wish I knew that less than a week ago. I’m working on a project that involves a finger hole on a cleaver. However, now I have another excuse to buy more tools. 😀
 

Drew Riley

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Another tip that should probably be mentioned/expanded on: Not every "oil" is suitable for drilling, cutting, or tapping. Contrary to popular practice, WD-40 is NOT a cutting fluid, unless you're using it for aluminum, in which case, it actually works quite well. Similarly, 3-in-1 oil and other motor and lubricating oils aren't going to be a much better choice. Are they better than dry cutting and drilling your steel? Sure.... maybe a little bit.

Sulfurized cutting oil is going to work 100x better for your average steel application. You can get a gallon jug of it at your local big box store's plumbing section for around $20 or less, and for the average home shop knife maker or machinist, it'll probably last you around 10 years or more. I like to keep some in a no spill oil cup with an acid brush, and/or in a little squeeze bottle with a small point. Just a dab'll do ya.

At the end of the day, proper feeds and speeds will trump even the latest and greatest space aged lubes and cutting oils, but when you have both, you'll start forgetting the last time you had to sharpen a bit.
 

Crag the Brewer

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I also thought of going with a cobalt step bit in order to finish the job, would this cut it if it’s work hardened? Or what about masonry bits? I’m pretty much willing to buy any bit right (as long it ain’t stupid expensive) now that will just get the darn hole drilled.
Only thing I know that will work on hardened steel is carbide.

It's very hard and brittle. Carbide doesn't like vibration, so I like to clamp down my work piece. It also helps to prevent the blade from sucking up, and spinning around like we always see on forged in fire.....haha/ugh. :/
 

Diego_B

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Well I ended up getting a cobalt bit and that did the trick of getting through the workhardend area. It looks like I need to learn a better drilling technique and I'll get my hands on some proper cutting fluid. Thanks for the tips and information everyone!
 
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