CNC Turning Hard Steel! WW112
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- Опубліковано 12 вер 2024
- Can we turn HARD steel? It's pretty amazing to do with a cubic boron nitride insert!
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Links for this video:
Example of a CBN Insert: amzn.to/2cmi0DY
Great Article on Hard Turning: bit.ly/2cmivxT
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Music copyrighted by John Saunders 5 Reasons to Use a Fixture Plate on Your CNC Machine: bit.ly/3sNA4uH
Dowel pins are usually case hardened further than the core is. It makes sense that they get softer as you remove material.
also the hardened shell on smaller pin is thinner then the bigger pin, so it didn't really matter how you machined it, just happened to be still on the hardened layer of the large pin.
Pete Brubaker ya I was just about to post That same thing.
John, I've been using these inserts for a while now. I always like to keep two on hand for "emergency" type jobs where you have to machine something hard, or, you trying to machine some hard weld. I've had to use them to machine some case hardened sprockets and they work good. Yes not too good for interruptions, but they do work. Light cuts and feed. Don't overdo if.
+Abom79 Would be good to see you using these boron inserts on a manual lathe as NYC CNC suggests it can be dangerous withoug going into details.
Iv had almost no problems using just about any carbide insert to turn case hardened sprockets. Cuts like butter
Hardened dowel pins are case hardened only. Not through hardened. So the reason your "losing the hardness" is not because of the heat generated into the part. It's because you have cut deep enough to get passed the case hardening and exposed the softer core material.
I was just about to say that beat me to it
What he said
4th
+1
Occams is correct.
It's like flying lava! Awesome!
dowel pins are case hardened, so the deeper you go the softer it will get
7:53 That's what she said! Sorry couldn't keep myself!
I'm surprised no one has reported this video for pornographic content
cylo lloyd the wife would rather I watch real porn...doesn't cost her as much...lol
Yes, you can machine ball screws. They are surface hardened, so can be threaded once you get through that surface...
Usually dowel pins are used to located something to something else and keep it there, while helping the bolts to keep said parts from shifting in any direction. So case hardened makes sense, if they were through hardened it would be like using carbide endmills as dowel pins...they would just snap off because it's hard and brittle. The case hardened takes the best of both worlds, hard on the surface help with were and damage, but still soft enough in the core to keep its torsional strength.
All I do is hard turn heat treated D2, work for a company that make parts for steel tubing mills. Everything I do is at 62 rc. You have no idea how much this video just helped me, thank you!
Just starting to set up my home shop and this reminded me to purchase a couple fire extinguishers. Great stuff...
pb552 Always worth while. also look for metal specific if you plan on doing anything in magnesium.
Titanium as well. My dad worked for Rolls Royce aero and titanium swarf fires were an ever present danger.
Ahhh! Judd! I remember emailing him and giving him a treat about 5 years ago! He's super awesome.
That's a heck of a machine you got there. I wasn't expecting the finish to be that good considering how hard the part was.
Great job.
Yes you can machine the bearing journals on ballscrews John. I do for all my cnc projects. Leaving the bearing diameter hard . And I anneal the bit where I want to cut a thread. You can buy CBN inserts for cutting intermittent cutting conditions. Round geometry is the best for that. Also just a plain old Ceramic insert will turn a ballscrew. At a quarter of the price. And they fit standard toolholders also. If you find CBN fun to play with on steel. Have a go with PCD on copper. Gives you amazing finishes. No more gummy turning on non ferrous metals.
As I was watching your vid I was thinking to myself "those pins are only case hardened and he is simply cutting through the case"......Then lo & behold you brought that up on your own near the end of the vid. The other commenters below are correct in that they are only case hardened. You could prove that by cutting one of the pins in half (probably need a cold saw or abrasive wheel to cut it-you'll rip the teeth right off of a bandsaw blade) and then run your file over the cut end. You'll feel it skip near the outer edge, but once you get in towards the middle of the part it'll bite in.
The reason that many pins such as tractor implement pins & the like are only case hardened is that the hard case gives you the durability & resistance to bending that you need, but the "softer" center gives you the overall resiliency & resistance to breakage you need. If they were hard the whole way through they could/would simply snap off under a shock load. The "softer" center acts like a shock absorber and doesn't allow the pin to shatter when subjected to a shock. This is the same type of setup used on train wheels.......the outer skin is hard as %$#@ so it doesn't wear or deform under the extreme weight & pressures they are exposed to, but then there is a center section of a much softer material that acts like a shock absorber.
Anyway.........LOVED the lava scenes, and this was a great vid overall. Keep up the good work bud!
An old tool-&-die-maker I used to work with was turning Inconel on a manual engine lathe once and I remember thinking how awesome the glowing chips flying off that was. Unfortunately, that is not even close to as awesome as the "flaming silly-string" chips the CBN inserts on hardened steel makes. Impressive. (Although the blue'd chips in the scrap bin looked much cooler than the combusted metal hair I'm sure you're left with).
For an interesting test try cutting an old carbide end mill, let's see who wins. Carbide will be hard all the way through. Or quench some drill but and don't temper it.
Craig
Now send the slug to demolition ranch!
Matt would love it :)
Pascal Robert got that right!
I used to work in a toolroom making forging dies, I very rarely got to machine a die before heat treatment so the hardness was anywhere from 45 - 62 HRC using iscar ceramic inserts. The hardest I've machined being 80 HRC using a CBN tool and from my experience I found that both ceramic and CBN incerts perform best when running dry (no coolant, fluids or paste) fast surface speed and slow feedrate. on a ridged enough manual machine I managed to turn a 5mm depth cut on a 54 HRC forging die
didn't have much success when facing to the centre of components with CBN or ceramic inserts as it would tend to chip the tip really easy and both tips are for hard material only, they do not perform well on soft material
CBNs are a synthetic diamond.
I had a customer that had to turn some railroad wheels that used to hold and engine up as the reshape the wheels on the engine. We did that with hot pressed ceramic inserts. The chips came of to form what was a glowing pile of "steel wool".
There is a ceramic insert made and sold by Sandvic that is whisker reinforced with Kevlar and made specially for turned hard parts with an interrupted cut.
Cubic boron nitride is exactly that, cubic boron nitride. It is in no way diamond. Diamond is pure carbon
CBN is a completely different material than diamond.
I do a bit of hard turning at work. the trick is to pre machine the pice, the ceramic inserts are not meant to take a 1/4 of material off of a face. you risk cutting past your heat treat if you go deeper than half the diameter of the work pice. if your worried about over heating the part run air to the tool it will help break the chip and keep the part cool. and run a couple flex passes, hard turning has a lot of tool pressure involved. and you can hard tread with carbide tooling up to like 55rc your tooling life will just go down the shoots
Are the pins losing hardness or are you simply turning off the hardened section? The part may only be surface hardened.
probably just case hard.
Sam yea they are case hardened so he is turning off the hardened parts
Yes, yes and yes.
@NYC CNC one thing you might not have considered is that hardness of parts has a depth depending on how the material has been hardened. Generally pins an such are only surface hardened so after you break through that heat treatment your left with the softer metal below. The only way to take the hardness out of the steel is to reach the critical temp of annealing, which is to heat the part or the surface of the part up to that 600F+ degree heat (look up actual temps somewhere).
Ballscrews are not typically hardened throughout. The core may be harder than CRS, but not as hard as the surface.
Back in the day we would take a large depth of cut as a rough cut (removing all of the interrupted cut) and then a couple of roughing passes and finish. All on manual machines.
We also have had luck with annealing the ball screw ends with a torch before machining.
Sounds right to me, through hardening is a relatively expensive process requiring all kinds of fun maths, specialized cooling systems and are restrained by the laws of physics whereas case hardening can be done reasonably well by anyone with a blow torch, a few cinder blocks, and a bucket of oil.
Essentially you are forcing metal to form a tight lattice around impurities/alloys, metal heats up, impurities dissolve into metal, rapid and even cooling locks it all in place whereas slow, uneven cooling pushes the impurities around and messes up that nice crystalline lattice.
So basically you'll always have a hard time with through hardening unless you've a way to cool the core down as fast as the outside of the metal cools, impossible for solid blocks of any real size, that's why a lot of hardened steels are case hardened or thin/hollow.
Don't take my word for it though, there's open source fluid dynamic software that you can use to simulate this. I used it to model my entire home foundry and get nasty letters from the EPA saying "we don't care what the science is this is the law, cease and desist or pay a $500,000 and spend a year in prison" :P
you can turn up to 55 ish RWC with regular carbide. Ball screws are not going to be overly hard otherwise they would be prone to cracking, so you can just turn/thread with regular carbide. Dowel pins are usually only case hardened so if you remove too much you will be through it into the soft core.
The reason for the burning chips isn't because the tool is heating the steel to orange hot, but because the chips are actually burning with the oxygen in the air.
The tool just has to add enough heat for the chips to reach the combustion temperature, which lowers as the thickness of the chip decreases.
If you have ever burned steel wool, you will recognize the behavior seen in this video. And if you never have burned steel wool, go get some Grade 0000 and try it! Lol
It is fun, and also useful as an emergency method of starting fires. It can be lit with sparks, with electricity (put some across a 9 volt battery for instance), etc, and it burns very hot.
I can't say for sure why it wasn't burning when you got into the softer stuff, whether it was creating less heat, or if the chip was thicker, or probably both, but a couple of times when the tool would hit the hardened steel at the end of the dowel and throw burning chips into the bird's nest (which is basically a pile of steel wool at this point), you could see the flame trying to spread, but it was too thick and too loose a bundle to stay lit, or it would have burned the whole bird's nest like a clump of steel wool.
And of you had squeezed the bird's nest down to bring the fibers closer and applied a lighter to it, it would have burned quite nicely.
if it reached like over 300°C martensite stucture turned to troostite or sorbite. It looses hardness depending on the temperature it reaches. actually after checking it - if it reaches 250°C it turns to bainite, 500°C to troostite, 750°C to sorbite structure. so you dont need much heat to damage the hardened steel. another thing is this thick pin is not hardened through whole thickness, but only up to 5mm on the surface. while the middle is much softer like 45-50hrc
Dowel pins are case hardened and not thru hardened. This is so they retain some elasticity, and won't break from an impact. You can increase your depth of cut to .015 to .03 per side. Sfm could venture into 1000 and above depending on grade and material being cut. Chip load can vary depending on surface roughness required.
10:41 " I wanna make some flame for fun" Love the excitement in that statement👍
CBN-inserts are either just a coating to a more flexible base or they are sintered into a matrix as far as I know. There are different ways to generate b-BN, most common is a chemical reaction of B2O3 + 2NH3 resulting in 2BN and Water.
The cool stuff about CBN is it's high-temperature-advantage when it comes to hardness: Yes, polycristalline diamond is harder at lower temperatures, but when it gets warm, the hardness drops pretty fast and pretty low. CBN also loses hardness, but slower. So if you get hotter and hotter, at some point (around 1000 °K), CBN starts to be harder than PD.
Chemical resistance at hight temperature is also better than diamond. Also it has a high thermal conductivity.
Disadvantage of CBN is like some said already: They like continous cuts and constant temperature. So you should use them without or with very few coolant, otherwise they will break, because of the thermal strain. You should also be carefull what materials you form with CBN, cause with some, there can be reactions (Copper, Silver, Chrome,...).
Good tip for using the phile, not many people know that. I do not like the position of the turning tool, it generates vibrations on longer pieces. Must be placed upside down, the insert must face you, and you see beter what is doing and most important you increase the rigidity of the mashine. Think about it: You have the tip of the tool. Rotation of the chuck makes presure on the tip who transmits the tresure to the tool holder and then the preasur goes to x axys. It ghets all the play from x axis if any. Correct me if i am wrong.
Unbelievable! Totally awesome the Tormach has that much rigidity. I didn't think it would, I thought you would break the insert. Wow. Really, wow!
CBN inserts have been around for a good while now.
Most likely you are cutting case hardened steel as 1018 is a low carbon steel, surface hardness will be around 60hrc ar surface but the depth will only be shallow on these pins.
CBN inserts don't work too well below 50hrc, thats likely to be when your swarf stops glowing.
Tip, when using CBN don't use coolant as it can fracture inserts.
Dowel Pins are usually only surface hardened. Ballscrews are too.. i machined a lot of ballscrews, the outer layer is hard, but as soon as you have removed the outer layer, threading was easy..
If you want to try something that is totally hardened, try an old endmill shaft.. I use those to make tools for the lathe, hardturning and hardmilling them..
And yes it makes sense that it wouldn't be through hardened if it's that dense, however you might find more expensive dowels for more, that might be through hardened.
I had to had to cut a gear at 55 Rockwell with a hhs cutter. That went nowhere quickly.
boron nitride has the same electron configuration as elemental carbon, so it forms all of the allotropes as carbon; cubic boron nitride is the same crystalline structure as diamond, as is tungsten carbide. If I'm not mistaken.
Yes, you can use CBN to turn ballscrews. I don't think you can easily get CBN threading inserts (too fragile, maybe), but generally you pretty quickly get below the hardened layer of the ballscrews I can afford to use, and then conventional threading tools are fine.
I have done it a few times now. I have a video on my channel of hard-turning a ballscrew on 1950s Colchester with CBN tips.
I have hard turned my tappetts for a couple of years and it works well even though I can't get the proper SFM. The ones I use the direction is very important as if I back up if it drags on the part it breaks the insert so I pull away on every pass just to be safe.
Old news now John, but those pins aren't through hardened.
I love the finish hard turning provides, however the trick isn't so much to remove material, believe it or not, most lathes will be capable of doing that, the issue is to bring it up to a particular size. I don't know if you miced the part, but a very good test is to hard turn (ie actually hardened material) to a particular size. In my experience deflection is an issue and it would be interesting to see how this machine coped with a real world problem.
This inserts can be used on regular steels and if you want to give them a go on 1020 etc run them REAL fast. Like flat out fast! I use cermets regularly and the finish on many steels is almost as good as what you saw on hardened steel.
BTW, I absolutely love the channel . watching you grow is inspiring to all young machinist. Way to go!
Very interesting video. It's a bit hard to find 60fps videos on this subject. Sadly, the technical aspects flies right over my head, and I don't think I will ever truly be smart enough to understand and grasp any of it, I just find the physical part of turning to be mesmerising and oddly relaxing. Thank you for posting these videos and doing what not many people are able to do.
Keep up the great work!
the hardening treatment according to the specifications of the design can penetrate to 0.6 / 1.2mm below the surface. This obviously depends on the quality of the base material and if it is undergone remediation before turning. the hardness in the case of hardening does not mean anything because you can get to relatively 56/60 HRC but the depth of hardening and of only 0.4 / 0.6 mm from the surface
I work gear wheels 18 ni cr MN05 hardened to 57 HRC which I arrive already turned, toothed and ground and I have to take them on the drill to make the seats on the crown in tolerance of + - 0.02mm ... the hardened surface is the hard part then once it surpassed that and a material is tough but not that makes you despair ... as in drilling use a center drill carbide at 90 ° included angle and make a hole to the center 0.2 more big toe and then I'm going to drill with a HSS in normal ...
the price of this gears is 500€ of once . expensive !!!
we turn hardened surface hardened and plated Rod stock daily using both CBN and ceramic inserts, with the ceramic we take 1/8 cuts off each side 1/4 total per pass but the ceramic require hardened material as they don't care for soft materials.
You can even use CBN to turn Carbide. Got an end mill you need to neck, stick it in your lathe and use a CBN insert. Not great tool life and you need to take 0.02-05mm cuts but it gets you there. Just avoid the flutes they don't like interrupted cuts. I would also recommend a manual lathe so you have more control and feel.
i turned my ballscrews for my cnc mill. used regular carbide but had to put a new insert for finishing passes. once you cut down enough you can thread it because its only case hardened.
the chip stream from that dowel pin was almost hypnotizing!
The key is to keep enough surface speed so the heat is elevated on the cutting tip. This will ensure the heat going out with the chip and cutting force not brake the tip of the CBN. In this case, one cut has been enough with lower feed rate and higher surface speed. The lifetime of the CBN has increased 4 times and the surface finish has been even better.
I forget to mention the dowel pin is normally case hardened so this is why the last cut with same feed and speed don't create same heat as the first cuts. Today some shops supply solid quenched to 63HRc punch pin in custom size with few diameters on stock and turning the punch pin to customer specification. Same day delivery any size!
Yes, totally agree, manufacturers only case harden to as little depth as necessary, also razor blades are tool steel welded to cheap steel, just the edge.
I think hard turning looks better then grinding. I just got done learning about this in class at SCC Milford, Nebraska.
Cool video! Dowel pins are usually just case hardened about .060. Try drilling through the center to test if it. Is thru hardened
There are different grade inserts for light and heavy interrupted cuts and there are hard threading inserts. I had an application where a part was rough machined then hardened and finished machined after hardening and tool life was excellent.
Yes, they make threading inserts for hard turning. However its an adventure to get the right depths of cut and feed.
Need to get the slow mo guys on that stream of chips. Looks so cool.
I turn hard radius knives with interrupted cuts. We use a ceramic insert. They don't usually last long, but they're much cheaper than cbn.
I think We used Silicon Carbide... we called the "diamond" inserts at Federal Mogul making pistons. Chip beakers, Bi cut... and was the most awesome insert I have ever used. When I went to the Korean plant, they kept them locked in a safe hehehehe
The biggest diameter the lower hardness inside. You can trust me. I was working in company(as QC and technology) making M140x8 bolts 850 mm long gradem 8.8 for ball valve for power plant. We had a big problem with quenching and tempering fi 140 bars to 34 HRC. But we made it ;)
ooohh pretty sparks :D I was a little worried the molten metal could hurt the lathe bed though ?
The chips are hot but they don't have enough mass to transfer a lot of heat to anything. I mean besides skin.
Those pins are soft, you can cut them with a decent carbide insert. I regularly hard turn parts over 60HRC with CBN its a fucking nightmare most of the time. With most tool steels you can easily get a mirror finish if its running good, but you have to have a really heavy machine, and a super rigid setup. Got a part that has holes in it, good luck, interrupted cuts will shit on your day. We even had seco come out and they said fuck it.
Ideally you want to see that red hot ribbon flying away from the part, your parts should get no more warm than they would from high speed milling without coolant. They can get warm to the touch but shouldn't be burning hot.
There really isn't much advantage in it unless you are trying to kill a slower grinding operation, or have a profile too complex to grind. There are a couple parts I make that have to have 3mm taken off every time they get reworked. Hard turning takes roughly 45 minutes or an hour.
Just to add to this, most of those pins are case hard, they will be softer in the center. Also, decent CBN inserts are not cheap, they run upwards of 70 bucks an insert. You can get CBN inserts in just about every common form. The ribbon is normal. As far as the glowing the harder material usually does, you can actually run the hell out of it for giant flaming wads of chips blowing everywhere.
You have to watch out, just a little bit out of the zone and those inserts fail. You can usually tell by bright white sparkles in your birds nest.
I do machine A2 and D2 and M4 with Somitomo cnmg inserts BN350 . most of my stuffs had interrupt cut . i do run 16-22 inch diameter with 400SFM and depth of cut .0065-.01 and feed about 0.005 . and with one insert i can finish plenty of parts . you should try them if you have lots of hard turnning .
but if they are not interrupt cut . i use Kenametal Ceramic Inserts .
It is only surface hardened but if you really want to test everything try it with coolant. From the surface down to 10mm. So 2 sets of complete experimentation.
You need to keep in mind that you can only harden material from the outside and as you dont know the hardness and depth of the hardenig process, you could have cut to deep into it.
the remaining hardness depends in the heat treatment and the type of steel. the speed of cooling of the surface is much faster than the core. or if it have a superficial treatment like cementation or nitruration or the combination cyanuration
but those treatments only gives like max 2 millimeters of depth soo i think maybe hardened superficially by a molten salt bath or after heating cooled a few seconds in oil and left in air.
they made that so it have superficial resistance to the wear and the '''''''''''''soft'''''''''''' core supports deformation and avoid cracking clean off. they do the same to the teeth of the gears but with cementation and heat treatment or only nitruration
The part is most likely case harden. This pins are machined to closed tolerance and then heat treated ( case hardens) and final ground to final dimension. as you cut though the center will get progressively softer.
*I'm a simple man; I see a dog I press like*
A spontainious idea of mine is that when you use a more shallow/thin depth of cut, the cutter puts in the same amount of energy into a thinner chip (less material), and thus makes it hotter and glowing.
Could be wrong, but it feels logical in my head.
Case hardening processes implies surface enrichment with carbon and/or nitrogen, i.e, carburizing or carbonitriding. That's why you only get those flames in the hard surface, mostly due to the extra carbon.
case hardened pins sometimes have a nitride coating on it that explains why it gets softer in the middle nitride is very hard so it will trow lots of sparks when you cut into it. then it will heat up losing its hardness property .so when you cut or turn that it will get softer ! so to avoid that run lots of coolant or oil onto it to keep it cool. this should fix the hardness change at least once the coating of nitride comes off.
ceramic is also really good for hard turning as long there is no interrupted cuts.
It is usually the case (sorry about the pun there). I read an article in a gun mag that they did a bunch of tests to see what would be the best kind of hardening, whether it would be through or case. They found out case was the strongest over all due to the properties of both hard and softer material working together.
All these hardened components generally have a case depth of around 0.8mm(0.03inches).Hence the hardness is lost after it more
*cutting it more
A handfull of inserts you say!. The last time i bought a couple of those, they were like 40$ each here in australia. How i wish i could have been there at IMTS.
So are we looking at buying a new lathe now?
Enjoyed the video mate. Howz nappy change duties going on?
The handheld Tsubosan hardness testers seem a nice way to estimate hardness.
Awesome video John! You should team up with The Slow Mo Guys and make a video. Super high frame rate footage of chips this hot would be incredible. Even typical turning and milling is super majestic way slowed down.
Case hardening +1, first thing that occurred to me before the turning even started. I would like for once somebody to show the actual hardness using a hardness tester - Yes an actual Rockwell machine (vickers or brinell also where apropriate) the file is such a poor test.
John, I have had punches hard turned (through hardened 60-62 hrc even 62-64) instead of finish ground, also form tools hard milled on a 4 axis cnc to remove the white layer after spark erosion, this can be much cheaper than form grinding and way more accurate than hand finishing.
CBN is brilliant for taking the skin off cast iron. Once the skins gone go back to carbide.
I have never through hardened dowel pins.
Hardness files from Japan also give you a good idea of hardness. Quickly
Should have filmed some with the lights off.
I looked at some dowel pins yesterday that were case hardened to 60 and thru to 50-55.
Rockwell pins are surfaced harden. used to work with the manufacturer many years ago...
It may have a case harden for the OD. Maybe softer in the center. All the hard turning was on tool and die work.
I hard turn 58-60 rc well for a living. I avoid cbn as much as possible, ceramic is the way to go it's a lot cheaper and it cuts better then cbn. The only time I use cbn is on interrupted cuts.
Why would you choose to hard turn? I mean wouldn't it be easier to turn something and then harden it? And doesn't the heat from turning something destroy the temper of the metal?
Sometimes the material you need to machine only comes in a hardened state.Induction hardened chrome hydraulic cylinder rod and linear shafting are two such items.
It can help with surface finishes and can be more economical as it may cut out some finishing operations and a need to heat treat the parts after work has already been done to them. Really limits the chance of critical features changing due to heat treat or scrapping expensive parts because of a botched finishing op.
Cool experiment John,thanks.
Passed the Judd inspection!
Dowel pins are usually just case hardened. This preserves their requirement on toughness.
i hard turn heat treated parts all day at work really nice when it starts a fire lol
Im turing a 31” long 2” dia piece of steel at 60 rockwell on a manual lathe at my work. If you get thru the hardened surface and into the soft stell you will damage that insert.
Hey I just watched "CNC Turning Hard Steel! WW112"
Hardened steel never has the same hardness on the inside. HRC is always particular high on the outermost layer.
You should really look into metal processing. Steel and aluminum are the most important. Especially with focus on phase changes. (there are many different physical processes that can affect strength and hardness, and heat treating is only a rough description)
I would sent you my scripts from my university but they are written in german..
try a through hard pin maybe 41/40. compare it to a hardened tool stainless pin, next try a hardened pin made from A2, D2, H13, CPM3V, or M2. That will REALLY test those inserts.
I use them to turn old end mill shanks into punches
also do an awesome job super finishing aluminum...
you should try it..... mirror finish right off the machine
The pins you're using are case hardened. Get deep hardened tool steel like O1 if you want to be sure that it's hard through.
The dowels are surface or case hardened usually they are carburised and heated and quenched in water .Only surface layer gets hardened More ever the process produces martensite structure which is and abrasion resistant But they not as hard as steel which is venedium carbide or nitrogen carbides I think it would be great if you use these hardened samples rather than case hardened dowel Pin
Try 90 Rockwell pins from McMaster... not easy. I used masonry bits for a .188 thru hole. 4, I used 4.
Dog is like, "bro.. that's NOT a biscuit.."
Those molten chips were awesome John
most dowel pins are only case harden for ware the root is left soft to prevent sudden failure. aka bend not break
I believe dowel pins are not through hardened, which would mean if you remove approximately 0.06" radially then you'd hit soft metal. Seeing the faster cut produce less spark was interesting.
Looking at the color of the chips as they leave the work piece it seems like the are actually getting hotter the further away they get. Based on this it seems likely that most of the heat you are seeing is actually a result of the rapid exothermic oxidation process, a bit like thermite.
You are correct. The iron is undergoing combustion. Thermite is different in that it is a single replacement reaction, where elemental aluminum is stripping the oxide anion from the iron cation. Producing elemental iron and aluminum oxide
I like the video, my only complaint on the file test you conducted was the following:
What was the hardness of the file, you should have chimed in.
The file test is just a general "is it hardened steel or not"
A rockwell test or a set of HRC calibrated file set would have been ideal to see the delta.
Also, is your dowel Through Hardened or Case Hard. There are two types, if the company was cheap in the manufacturing process, it might be "through Hard" but not really
If you have a FLIR you can see if your cutting at a temperature that is in the annealing range. If your concerned about hardness you'll have to flood cool, but I think you'll suffer performance.
Overall neat stuff.
Knowing that you don't use coolant for the sake of the audience. Running with coolant will help with keeping the hardness in the material.(and longevity of the cutting bit) Yes some carbide bits dows not like coolant. Just saying ;)