Lubricant for general hobby machining.

[B2]

This has never been clear to me if you want chips or spirals. Many on this forum seem to indicate that proper cutting results in chip breaking. However I do find the spirals to be a thing of beauty! Others seem to consider them a hazard. I suspect that some of the chip breaking is due to friction and binding between the tool and the cut piece (chip) and that some of this friction and breakage is removed due to some lubricants. Some chip breaking tools seem to bend the spiral sharply effectively breaking the spiral by bending it to induce stress/strain.

If you have done much drilling with a two, or more, flute bit, you will notice that sometime, but not often, you can get two spirals at the same time. One comes from each of the flutes. A thing of beauty! I interpret this to mean two things. 1) The bit is properly sharpened such that the two flute cutting edges are near identical! 2) The feed rate and rpm is adjusted such the each flute is cutting the same amount of material. If the two flutes are not sharpened evenly and/or the feed rate is too slow, then only one edge cuts and the other just rubs generating frictional heat and wear. ( For me, in hand sharpening a drill bit it is almost impossible to get both flutes to be exactly even, the same. This is especially true for smaller bits. So when I am calculating my feed rate I commonly assume that there is only one flute cutting! )

At a conference I attended, I wound up having lunch with a couple of research physicists who worked for Gillette. During our conversation I ask them to explain cutting to me. What is it that happens at the molecular level? How can I make a tools edge so sharp that it slices between the atoms to separate them. While there are models and theories, their response was that "no one really understands this!" What I know is that a new razor blade does not pull at the whiskers while an old one certainly is not as pleasant. By the way, is shaving cream a lubricant or is it just to allow water to soak into the whisker, swell it and to soften it up for cutting?

PS. Sometime you might want to try to measure the thickness of one of those spirals and see if it agrees with what you thought you were going to be via the feed and speed calculation.

Dave

 

[maticulus]

This has never been clear to me if you want chips or spirals. Many on this forum seem to indicate that proper cutting results in chip breaking. However I do find the spirals to be a thing of beauty! Others seem to consider them a hazard. I suspect that some of the chip breaking is due to friction and binding between the tool and the cut piece (chip) and that some of this friction and breakage is removed due to some lubricants. Some chip breaking tools seem to bend the spiral sharply effectively breaking the spiral by bending it to induce stress/strain.

This change in chip size occurs on the fly during the same cut. I start with brushing on the combination and in the middle of the process spray a little WD40 on and the chip shape change is immediate, so speed and depth of cut are consistent. It is repeatable. Measuring or examining under magnification is a good idea.

 

[Janderso]

I used A-9 for aluminum and Rapid Tap for everything else. Mostly to extend the life of my cutting tools.

Man that Rapid Tap makes my lungs hurt. It's good stuff for threading but I can't tolerate it heated.
Am I the only one?

 

[maticulus]

Man that Rapid Tap makes my lungs hurt. It's good stuff for threading but I can't tolerate it heated.
Am I the only one?

That's the kind of thing that scares me about chemical odors, some of this stuff is fat soluble meaning it can be absorbed through the skin/tissues where it can collect in the fat tissue and cause problems later in life. My father developed chronic pancreatitis (horribly painful disease) in his early 50s and had to retire early. It is a horrible disease often brought on by alcohol use and or high triglyceride levels (cholesterol related).

He smoked and drank as a young man only up until about age 25 then he quit never to take it up again. He was also a motor head hobbyist and did just about everything. I feel that his problem was partly promoted by all of the chemicals he had been exposed to at home and on the job, where he worked as a welder in a train yard repairing box cars. There's a lot about the dangers of everyday exposures that were not revealed until enough people were adversely affected by them and a link between the afflicted was discovered.

If it smells, I get away from it.

 

[B2]

This change in chip size occurs on the fly during the same cut. I start with brushing on the combination and in the middle of the process spray a little WD40 on and the chip shape change is immediate, so speed and depth of cut are consistent. It is repeatable. Measuring or examining under magnification is a good idea.

Yes, I understood what you said about the instant change in the chip vs spiral. This is why I suggested that the friction between the cutter and work surface is in play as to the cause of the chip breakage. It would seem that the WD40 interface has less friction. Also there is the concept of stiction as opposed to friction. Here the two surfaces do not smoothly slide along at a constant friction force, but "stick and slip" in a sort of jerking motion. This might be more likely to produce small chips than a sliding spiral of cut material.
This picture would say that the chip vs spiral is not just occurring due the cutting process where the layer separates, but also in the short distance (after the cutting edge) from the cutting edge where the tool is still in contact with the cut material.

Another thought, you might examine closely the cut surfaces and compare them. Surface that resulted during the spiral cut vs the surface that resulted during the chipping process. High quality magnified, or even none microscopic, photos would be interesting to see. Is one surface smoother than the other? Likewise, examine the spirals vs the chips. Spirals commonly have somewhat regular undulating surfaces or kinks. Is there any correlation between distance between these deformations and the size of the chips?

One of the problems with trying to understand these fluids is they are commercial. As mere consumers we do not have a clear picture of what the concoctions of WD40, the Harbor Freight foam, or others are made from!

In fact your observation "This change in chip size occurs on the fly during the same cut. I start with brushing on the combination and ..." is even more complex because the WD40 is being put on after the other lubricant has been applied. Does the WD40 mix with or does it replace the first lube or what? Observations like yours are tantalizing and fascinating as they clearly indicated a considerable change in the physics/chemistry/mechanics of the materials and process. Sometimes they result in a new and better product (invention), but other times they result in so many additional questions that one never gets a full understanding.

Anyway, keep at it we all want to know the answers and who knows maybe you will come up with a new formula for lube/coolant and become the next HM millionaire !!!!

Dave L.