Today we’re going to analyze the drill that broke last week while drilling in aluminum. We’ll take a look at it under the microscope, and then take advantage of a friend with a Scanning Electron Microscope to look at the morphology of the break, and do some elemental analysis. Because science. Also, because Clough42.
The drills in question:
Drill Hog M42 Cobalt Drill Set (Amazon*): https://amzn.to/3ore9sq
Tools used in this video:
Andonstar AD407 Digital Microscope (Amazon*): https://amzn.to/2Wh6rFY
Sony a7 III Mirrorless Camera (Amazon*): https://amzn.to/364DkpQ
Sony FE 90mm f/2.8 Macro Lens (Amazon*): https://amzn.to/2LBs9eQ
Neumann TLM 102 Condenser Microphone (Amazon*): https://amzn.to/3mPdiDE
Universal Audio Apollo Twin DUO Audio Interface (Amazon*): https://amzn.to/42heNLg
DJI 2-Channel Wireless Mic System (Amazon*): https://amzn.to/3ZNJOER
*These are affiliate links. When you click one of these links and make a purchase, it helps to support projects like this one.
00:00 Introduction
01:04 A broken drill – I make them myself
03:18 Under an optical microscope
05:01 Into the Scanning Electron Microscope
09:30 Morphology – Structural analysis
12:50 Elemental analysis
16:31 Conclusions
Raw Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0 License
http://creativecommons.org/licenses/by/3.0/
elemental analyzer, ductile fracture, defect analysis
source
Interesting; I had the exact same failure on some bits from them. One happened so quickly that you could see the coating over the crack. This was about 1 year ago when I had this issue, I haven't tried doing a warranty for the bits since I have broken so many, they would almost need to send me a new set.
"if you've ever broke a drill" yes
"On the lathe" no
"most of what's in my head got there because I'm curious"
That sounds familiar, school taught me nothing
Sounds like ADHD hyper-focus to me. Don't ask me how I know LOL😅
9:37 Right there, at the bottom…. The post-it on the screen…. ctrl-alt-del….
Does this thing let you reboot your drill bit? Asking for a friend.
Great video again, James. Careful with that autodidact thing in public, depending on jurisdiction and local laws.
I love the break-down and to have it end with 'so what are we going to do?' "Nothing" I found somewhat humerous considering. Will be looking at your other videos after this!
Cheap made in China fake quality. Even send you 10X replacement they still make good profit
Congrats on crossing over 100k subs! This was a great video for that occasion
Interesting.
Nice video! :o)
The channel Breaking Taps has an electron microscope that can identify elements on a per-pixel basis, and make a grid of images of where each element is located. For example in his Metal Alloys video. That way you can verify what the granules actually are.
Seems like the operation you were doing bent it.
I'm not an expert either but I did stay at a Holiday Inn Express last night and I concur with your hypothesis.
This was a great video. Failure analysis is such a fun road to go down. As a retired rocket scientist I have had the opportunity to be involved in a number of Failure Analyses, some with catastrophic (and adrenaline inducing) events. My favorite event was watching ceramic catch on fire. Cheers!
Thank you for an interesting and thought provoking video! I find that the most significant problem with the autodidactic approach is that there simply are not enough hours in each day, particularly when you have to exchange a portion of those hours in exchange for money. 🙂
Ah, micro-cracks: those horrid things that are almost never found before it's too late. Seeing that one can silently and stealthily sit in a drill through use in multiple projects before becoming a failure point makes me sympathize with aircraft and bridge engineers all the more.
EXCELLENT!! It's a crying shame more high school and college science teachers weren't this fun and educational!!
Looks like some coarse beach marks just behind the end of the oxidised flaw indicating a few cracks extension cycles before brittle failure.
Excellent explanation on SEM and EDAX analysis ( I assume this was the analysis method). I have worked with SEM, but on a very basic level.
It would certainly appear that the drill bit was cracked during manufacture.
Thanks for sharing
See, your problem was that you were trying to enlarge into a pre-drilled hole. You should always try to enlarge a non pre-drilled hole, it works much better 😉
Nice to know where to look if something is broken. The centre of the drill is pushing the metal away, so forms a resitance to the drill, preventing that drill is digging into the metal. You see this also happen if drill through a metal sheet, as soon the centre point is through the metal it will grab the metall because there is no counter force any more and the backslash of your drill press will make it worse. So on soft metals it is better not to pre-drill with a smaller drill. But in your case, just a bad drill in on a bad day.
0:31 "autodidact" (αυτοδίδακτος)…. OMG you speak Greek….
Anyhow I always enjoy my watching your videos…
8% cobalt drills are a brittle and not suitable for Aluminium. They are for harder steels and stainless. Get a cheap set of presto dormer or guhring HHS drills. I really enjoyed this brought back my days of using stem and tem. Had the same years ago with someone who had an old Japanese knife that broke, in with a loupe and you could see the impurities in the steel. He was non too pleased when I told him he had in his head some multi folded hand crafted best knife in the whole world .. just with a few impurities. 😂
Excellent video! Always learning something watching your videos. Thank you!
You continue to surprise. That is quite an analysis! This level of metalurgical analysis is not common to home shops! Lots of great comments below, but I have routinely drilled a smaller hole, then a larger one. Aluminum is soft, with good control of the feed, a decent bit should handle the job. It is true, though, that machinists routinely cut aluminum with carbide bits at very high rpm, which would minimize the depth of cut per revolution.
Very cool analysis! Every machine shop should have an SEM available for this kind of deep-dive! 🙂
I spent a few years in a machine shop that's been in business for around 60 years. It was pretty standard known not to enlarge holes with a drill if you have any other option to enlarge the hole. I was taught the tip grabbing into the material does a lot to hold the drill centered. That when a hole is enlarged, it can cause vibration in the drill which can uncenter the drill causing a higher force the flutes can't handle
Very interesting failure. Many years ago I was given a box containing hundreds of new drill bits labeled as rejects by the makers. I found the same faults in all of the ones I tried to use.
Looks like your example missed the test.
Almost every metal failure shows the reason in the fracture surfaces including polished surfaces deep inside where voids have been moving.
Two flute drill bits shouldn't be used to enlarge holes for the same reason that two flute milling bits shouldn't be used to cut slots. The forces on the flutes will always be out of balance, leading to vibration and a tri-lobular biased hole shape. As others have stated, you want a good deal of the point width to be cutting to minimize that issue, because once you only have the tips making contact, it gets pretty bad.
As a rule of thumb for boring with drill bits and stepping up sizes, you can safely start out with a hole that is smaller than the web thickness of the next drill bit you plan to use. So, for a 1/2" bore, you can drill first with around a 3/16" hole.
And as for the operation you were performing on the lathe, well you probably should have been using a boring bar. Also FYI, that works better upside down and in reverse.
And yes, your bit was probably cracked during heat treatment and was defective.