Why Does Cutting Fluid Work? - Page 3
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  1. #41
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    Quote Originally Posted by CalG View Post
    Bob's point is most valid.

    This is the only video sequence of it's type that I have viewed that DOESN"T show a pronounced gap near the cutting/contact point.

    Consider a Built up edge condition. The space comes from somewhere.

    "The edge of a sharp knife never touches as it cuts"
    That video is sort of cool in that someone took a LOT of time set it up in an electron-microscope; using backscatter mode heavier atomic weights show up as lighter contrast, so a second-phase can be seen in the "stock". However it doesn't have info on the materials, cutting gemometry and conditions, etc.). Seems it would be very difficult to correlate or set up any test in an electron microscope to real-life cutting conditions. It would be interesting to see their "setup" and conditions for those electron microscope movies, skiving a chip off in a microscope doesn't bear much resemblance to hogging a cutter at thousands of rpm.

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    Here are some more microscopic videos that show a variety of typical conditions. They also state what the material is.

    YouTube

    Note in all of them how a built up edge continuously forms, only to break off and get smeared under the tool. The third segment is particularly interesting; the chip welds to the tool, and the chip that now can't slide up and off the tool has all sorts adverse effects on cut quality.

    I agree with the OP; slathering cutting fluid on the top surface of the work is certainly NOT putting it where it's needed, it only puts it in the general neighborhood. It's just luck that enough spills around the sides of the tool to get where it needs to be, but the improvement noted with use shows that we are indeed lucky more times than not.

    Dennis

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    I learned a lot in this thread. Too many good posts to give each of them an individual like, so thumbs up to all of you!

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  6. #44
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    While the videos posted by npolanosky look very much like actual electron microscope footage, this video, posted by out OP, ptsmith, is clearly a four second loop. The same features repeat over and over again and there is no apparent discontinuity in the video. That lead me to think that it is an animation. HOWEVER, a careful examination of the first video posted by npolanosky reveals that the OP's four second loop was taken from it. I can only conclude that the person who made the loop did some very careful editing.

    The two electron microscope videos posted by npolanosky seem to support the ideas that I posted above. I also liked the post that said that "... Tricloroiethane 111 did wonders cutting steel, it was super wetting, by which I mean it flows into crevasses and is much thinner than water." That also seems to support the ideas that I posted.

    The cutting fluid may not get to the actual point where the cutting is happening in all cases, but it would appear that it can get very close to it. And in the second video posted by npolanosky it appears that the point of the cutting edge is actually clear of the material being cut for short intervals between when two pieces of the chip are broken off. That separation along with the fractures between the pieces of the chip would certainly allow a fluid to wick up in there.



    Quote Originally Posted by ptsmith View Post
    I did not present my question clearly. Let me try again.

    Cutting fluid is on the surface of the part being machined. The actual cutting happens below the surface. There is tremendous pressure between the cutting tool edge and the material being removed. How does the cutting fluid get from the surface to the leading edge of the cutting tool?

    Think of peeling an orange that's covered in grease. The finger that's under the orange skin is shielded from the grease and could peel the entire orange without getting any grease on it.


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    I can't give any scientific data or any microscopic video to prove or disprove weather the cutting oil makes to the business end of the tool. My opinion is no or at least very damn little makes it up to where the cut is happening.

    I think they used cutting oil back in the day when that's all they had. I don't think putting oil on with a brush actually does much of anything but maybe cool the work off a bit and doesn't do all that good a job of that. It just makes a smoky mess.

    This passed April I've been doing this kinda work 31 years. I can count on one hand and have a couple fingers left over as to how many times I've seen people use cutting oil in the shop. The last time I used cutting oil was running a small Southbend when I was in high school.

    If I'm at the Hardinge lathe I rough mostly dry. I try to keep it from getting too hot by squirting it with a squirt bottle once in a while. I fill my bottle up with ice then fill it the rest of the way with coolant from my machine. The ice makes the coolant really cold and it doesn't do bad keeping the part cool.

    Over at the engine lathe it has a sump filled with coolant. The nozzle is mounted right on the carriage and follows right along with the tool and keeps the part fairly cool.

    If you have the part hot enough you can touch you can't measure it with any accuracy due its gonna shrink. So then you're waiting around waiting on the part to cool so you can get a decent measurement on it for finishing.

    I guess my point is IMO it doesn't matter because ain't nobody using cutting oil in a modern shop. We don't even have any cutting oil. Lol...

    This is all my opinion so take it for just that.

    Brent

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