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OT. Professor Phil Moriarty (nottingham university) on gauge blocks

It was rather funny watching him trying to wring them, guess the wonderfully talented technician didn't show him how.
Mark
 
I think the technician did show him, he just needs more practice.

His explanation is as good as any that I have heard. It has some rough edges, like when he tries to explain why they need to be real flat, so he could refine it somewhat. I suspect that if the surfaces are not real flat, then there are, atomically speaking, large distances between the atoms of one and the other and those forces drop in strength by the inverse square law. With a rough surface(as), the atoms are only close enough to each other at the peaks where the two surfaces do touch and those have a relatively small area. So the amount of attractive force is much less.

I believe that this and friction at least partially share a common explanation.
 
These effects are interrelated. In a Russian book on triboelectric effects they invoke the photoelectric work function. Two materials in contact are not just sitting there, each within its boundary. They are trading electrons and bonding together. Glass has one of the highest friction coefficients. I once made a feeder for small glass tubes that worked well with the samples the customer supplied but when we used new production, it jammed up. The explanation was that the samples had been handled and had a finger oil coating that let them slide while the new production was very clean.

Bill
 
WTF????

An explanation on gage block wringing by someone who's never seen a gage block before, demonstrating on a gage block set that belongs in the trash.

A chimp at the zoo could have produced a better video.
 
NAST555 said:
Why so...?
Click to expand...

Not to mention the fact that the blocks will not properly wring. They are probably either scratched up or no longer as flat as they should be. I lost count of the number of times he tried to wring them and failed. Didn't help that he was doing it all wrong at first. I was taught to bring the blocks together at 90°, slide them until they're centered like a plus sign, and then twist them into alignment. Mine wring first time every time.

I've read that the wringing occurs due to several reasons combined - Van der Waals forces, slight vacuum between the blocks due to the exclusion of air, and surface tension due to the presence of a thin film of oil or water vapor.

Edit: here's a link with info from Starrett:

http://starrett-webber.com/GB46.html
 
Larry Dickman said:
Look at the set. They're all stained and rusted. garbage
Click to expand...

I think I was more worried about how he struggled than looking at them so well spotted. Re-watched it again and paused, they sure are in bad condition... I was just worried that you meant because it was a bad set to start with. I have a similar set just in smaller increments.
 
Heck, and I was quite happy with the covalence explanation, that electrons are momentarily swing into orbit around the closest atom next to it's parent atom, and visa versa.

This though I can't visualize, Van der Waals, like a form of super electron magnetism on an atomic level?
The forces have been quantified, they are many times what vacuum can provide.
 
Larry Dickman said:
WTF????

An explanation on gage block wringing by someone who's never seen a gage block before, demonstrating on a gage block set that belongs in the trash.

A chimp at the zoo could have produced a better video.
Click to expand...

That was exactly my reaction, I couldn't believe that the guy couldn't just say the blocks are wringing? And the answer is because he doesn't actually know that, although he's a smart "professor", he goes into molecular structure...yada-yada-yada

Pretty common knowledge that the surface needs to be less than approx. .0005" in order to wring, so beat up gauge blocks will not do it no matter what. I also noticed he was using acetone to clean them which is fine, but I find rubbing them on the inside of my wrist works better, or the crook of my neck, or forehead. Those are oily areas of our body.

Kind of reminds me of the inet, a guy that doesn't really know what wringing is describes it to the world using physics and other complicated terminology as he doesn't really know what it is he's describing. :wall:

FWIW, Don Bailey has a video where he talks about gauge blocks that I find more informative, although he doesn't talk about the physics of how it works when they wring, he does use the oil from his wrist after cleaning them. The "professor" cleaned the blocks with acetone which remove all the oil, but doesn't wipe them on his wrist, neck, etc... Anyway, not to beat up on the "professor", but listening to a guy that learned what wringing is by talking to a machinist 10 minutes ago, and now does a video on the inet is slightly annoying. :rolleyes5: I have always felt comfortable that Don Bailey knows what he's talking about, from experience. :)

 
Until recently I'd never heard of human oils or water or anything else being involved at all. The little hard Arkansas stones sold to dress blocks seems like a waste of money for carbide and ceramic blocks, which should be too hard to raise any burrs on.

The deeper message of all these discussions seems (to me) to be that no one really understands why they wring with the separation resistance they have, even when they try to explain why they do.

In that regard it appears to me to be like many electro-magnetic-radio-light discussions, all theory about phenomena that work, but the theories only help understanding while not being provable.
 
I think probably no one cares enough to investigate it further, heh. Which is kind of silly if you think about it.

I would guess that the reason the force to separate the wrung blocks is higher than can be explained by any one factor is that there is a combined effect from the different forces at play. So vacuum probably plays a small role but certainly isn't all that's going on. And the blocks need to be flatter than 5 microns or ~ .0002" - not .0005" - or you will start to have difficulty wringing them tightly.
 
The problems weren't due to the perceived state of the gauge block set. They were almost certainly because he initially had some contamination on one or both of the blocks due to using a paper towel to clean them with.
 
We had a permanent set up on a sine table, after a cople of years the slips welded together, ripped chunks out of each other breaking them
Mark
 
after a cople of years the slips welded together, ripped chunks out of each other breaking them
Click to expand...

I've heard of that before. Pretty amazing isn't it? You could weld over time based only on perfect contact areas, though probably never more than a partial weld.
 
Many, if not most, metals will pressure weld. They don't in normal service because they have a film of oxides and other coatings they pick up. In space they often boil off leaving clean surfaces that bond. This is a serious design problem in spacecraft. Gold pressure welds in our normal atmosphere because it does not oxidize.

I rarely watch these videos because the perpetrators seem to be in love with their voices and go on and on instead of getting to the point. As Robert Blake said about acting, "Just hit the marks and say the jokes."

Bill
 
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