# Heat Effects on Spirit Levels



## vtcnc (Nov 25, 2021)

Found this on Instagram this morning. Pretty interesting and disturbing at the same time.









						Instructor Adam B on Instagram: "4 Things You’ll Wish You Didn’t Know About Levels - Part 1  Digging ever deeper into the surprising world of spirit levels, I stumbled across a few bizarre phenomena which affect level readings  There’s so much intere
					

Instructor Adam B shared a post on Instagram: "4 Things You’ll Wish You Didn’t Know About Levels - Part 1  Digging ever deeper into the surprising world of spirit levels, I stumbled across a few bizarre phenomena which affect level readings  There’s so much interesting stuff here I had to split...




					www.instagram.com


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## RJSakowski (Nov 25, 2021)

My level is encased in about 2 lbs. of iron which will go a long way toward eliminating the thermal effects.  Interesting though.  Metrology labs never make precision measurements or calibrations without allowing a devise or an object to normalize to the room temperature.  My shop is fairly well temperature controlled, never varying by more than a few degrees year around.  A  garage shop would be an entirely different story.


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## RJSakowski (Nov 25, 2021)

Items 3 and 4 would be a non-issue.  Level would be defined by your particular location.  Level as defined by a plane perpendicular to a plumb bob or to a plane parallel the surface of a liquid wouldn't measurably change over a short distance.  It's a known fact that a nearby mass such as a nearby mountain will pull a plumb bob towards it but all measurement will experience the same effect.


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## tweinke (Nov 25, 2021)

That was very interesting. Makes me wonder how many people leveling a machine could have been bitten by the heat bug while trying to get good readings.


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## vtcnc (Nov 25, 2021)

tweinke said:


> That was very interesting. Makes me wonder how many people leveling a machine could have been bitten by the heat bug while trying to get good readings.


That is what I found interesting while thinking about this as well.


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## sdelivery (Nov 25, 2021)

I am a professional who has used his spirit levels for decades.
I always give my instruments time to acclimate to the temperature of the object by placing them on the machine..
I have seen a  garage door opening and closing change my level.
I have seen guys wipe the dirt off the vial of a starrett level and change the reading!
Like most tools there are idiosyncrasies to achieving accurate results.


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## tweinke (Nov 25, 2021)

All so very true. Mear mortals like us home shop/ beginners forget to apply all the factors to things that a true professional does as a matter of course. That is why i like to come here, the knowledge of the guys here can solve problems that are overlooked by those that do not know.


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## sdelivery (Nov 25, 2021)

Mear mortals! Luv it!
Aren't we all ? Just in different venues?


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## graham-xrf (Nov 27, 2021)

RJSakowski said:


> Items 3 and 4 would be a non-issue.  Level would be defined by your particular location.  Level as defined by a plane perpendicular to a plumb bob or to a plane parallel the surface of a liquid wouldn't measurably change over a short distance.  It's a known fact that a nearby mass such as a nearby mountain will pull a plumb bob towards it but all measurement will experience the same effect.


Yup  - this happens! My Dad (builder) had a traditional lead plumb bob set into a "teardrop shaped" cutout in a hardwood plank, and with a fine V-line cut into it. The whole thing, which stood as high as a man, had a cover box that could be removed sideways, with viewing aperture, all to stop air disturbances. He told me the same thing about Table Mountain (Cape Town). The middle of that peninsula mountain is made of iron, or something dense, because all the buildings stand slightly off true geographic vertical, and plumb bobs hang slightly pulled toward the mountain.

Not a problem for building purposes, because the forces in the buildings are still properly catered for by regular spirit levels.  I expect any satellite tracking dishes in the region would have to correct for clinometers being somewhat untruthful. The messed up way levels worked in Cape Town has been well known since back in the 19th Century because of the importance of the Observatory in Cape town, and the huge efforts to establish the Southern Arc of the Meridian, and prove the Southern half of the Earth oblate spheroid was the same shape as the Northern half.

The deviations from vertical were known as "La Caille’s discordances". I am not sure it is true that at the base of the mountain, coffee in a cup will look slightly skewed off level. I never noticed anything like that, and I lived for a while in a University residence on the slopes of Table Mountain.



Great history and pictures here -> Arc of the Meridian Survey


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## addertooth (Nov 27, 2021)

I am so sorry, but you summoned the physics genie.   
Yes, mass, height from center of Earth, and time all impact gravity (and perceived level).
I worked in a physics lab for a lot of years.  It is a well proven maxim that a large mountain nearby can create a sideward pull. 

Now for the real mind-blower, which has been well-proven by experiments.  Time on the surface of the earth is slower, than time up at the distance that geostationary satellites orbit.  

Now for the more significant issue.  Level is not as critical as you think, as long as you are not introducing a bow or a twist in your machine tools.   There are lathes and mills on heaving and bounding ships, which still produce very accurate bearing surfaces.  The lathe on my SEORTM (gooney-bird, Batmobile), was quite accurate, but almost never level (The SEORTM is a machine shop on an extended 5-ton Army truck).


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## RJSakowski (Nov 27, 2021)

graham-xrf said:


> Yup  - this happens! My Dad (builder) had a traditional lead plumb bob set into a "teardrop shaped" cutout in a hardwood plank, and with a fine V-line cut into it. The whole thing, which stood as high as a man, had a cover box that could be removed sideways, with viewing aperture, all to stop air disturbances. He told me the same thing about Table Mountain (Cape Town). The middle of that peninsula mountain is made of iron, or something dense, because all the buildings stand slightly off true geographic vertical, and plumb bobs hang slightly pulled toward the mountain.
> 
> Not a problem for building purposes, because the forces in the buildings are still properly catered for by regular spirit levels.  I expect any satellite tracking dishes in the region would have to correct for clinometers being somewhat untruthful. The messed up way levels worked in Cape Town has been well known since back in the 19th Century because of the importance of the Observatory in Cape town, and the huge efforts to establish the Southern Arc of the Meridian, and prove the Southern half of the Earth oblate spheroid was the same shape as the Northern half.
> 
> ...


The effects of any nearby mass would be negligible for all practical purposes.  In any event, a plumb bob and spirit level would experience the same forces and should agree.  The effect of the gravitational pull of the sun and moon would be greater as evidenced by ocean tides.  Any edifice constructed near a very large mass such as a mountain would be plumb and level to the eye but in actuality, it would be slightly askew.  There would be no simple way to check this as any reference would see the same effect.  One possible way would be by observing the position of astronomical features although this would require very precise time measurements.  An interesting thought.  

There has been some locations where whole mountains have been leveled due to mining operations.  Any edifice would now be leaning slightly away from the missing mountain.  I suspect that the change would be insignificant.  Certainly, we wouldn't be able to observe the effect as our internal plumb bob that allows us to observe the vertical would see the same forces.

An interesting experiment would be to level a stable surface with a sensitive level and obser4ve any changes over time.  These changes, if any, could be compared with the position of the moon and the sun over the course of a month to see if there was a correlation.


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## graham-xrf (Nov 27, 2021)

@RJSakowski
I did think the deflection would be negligible. It seems not negligible enough for the surveyors doing the Cape Flats baseline, nor for the baseline on the Grand Parade Square. You are quite right that it does not affect our use of spirit levels at all! Who cares if the downwards pull is not truly at the Zenith, so long as it is the same over the whole thing the level is on.

I am always surprised at how non-intuitive is my appreciation of the effects of gravitational attraction. The way warships parked next to each other will supposedly "pull together" over a couple of days (do they?).

I still have a couple of old videos taken in a university basement, of a qualitative gravity experiment using what looks like boule game steel balls, also called la pétanque.  The time lapse was triggered remotely with nobody in there, and all sorts of care taken to eliminate air disturbance, but the actual kit was just hung under a stepladder. I am not sure what was used for the suspension, maybe fishing line or fine thread of some kind.
Check the timeline. It took hours!

View attachment Gravity1.mp4


View attachment Gravity2.mp4


For our purposes, deflected or not, we only need levels to provide a handy (intangible) reference so we can go measuring along surfaces, and discovering the actual dimensions and wear on our machines. We choose horizontal, but in theory, if we decided to always use the level some constant amount tilted, we can still do the measuring job, only having burdened ourselves with extra arithmetic, and that would be a truly nut-ball thing to do.

*Temperature effects?*
Lacking a really good straight edge, I am grateful that I can work my way along the ups and downs of a worn surface with a thirty quid Chinese level claiming 0.02mm/metre, or about 4 arc-seconds angle sensitivity. The levels do not seem to care about being near freezing sometimes.
BUT..
The situation might be different for the ways of a knee mill if it has been in a below freezing shop all night, and then experiences a significant temperature gradient. You get the heat on, and start milling madly. The motor heats up, etc. Maybe the bed will start to curl. I guess the way to see it would be to try for a video with it illuminated by monochromatic light, taken through a diffraction grating, or some such hologram-type tricks.


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## vtcnc (Nov 27, 2021)

I think it is worth stating the following for newbies who are wondering why any of this is of interest to hobby machinists.

My understanding about the topic of “leveling” a lathe has always been NOT to level the machine in the purest sense of the word, but rather to remove TWIST. 

If leveling were the key to a successful use of the lathe then there would be no such thing as a vertical lathe, or for sake of discussion, vertical boring machines or milling machines.

Twist is our enemy not level. That is why mills need to be trammed. 

With that said it makes perfect sense why we have to be mindful of temperature effects on the spirit level when removing twist from the lathe bed.


Sent from my iPhone using Tapatalk


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## tweinke (Nov 27, 2021)

This has been very interesting reading so far. All good information. Metrology is a very interesting subject


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## graham-xrf (Nov 28, 2021)

vtcnc said:


> I think it is worth stating the following for newbies who are wondering why any of this is of interest to hobby machinists.
> 
> My understanding about the topic of “leveling” a lathe has always been NOT to level the machine in the purest sense of the word, but rather to remove TWIST.
> 
> ...


You are right in that there is nothing absolute about mounting a lathe "level", and I did say that the value in "leveling" was only to have easy access to an external reference to measure from. Lathes can, in principle, be mounted in any attitude, so long as where it is does not eventually introduce any self-weight distortions or twists.

It's an incredibly convenient intangible reference, and we get there with a spirit level. Lathes mounted on ships can hardly be ever be "level", but when they are securely attached to the ship, they use the ship's line reference for the day. It may not be truly horizontal at the time, and keeps changing during construction. Again, the handy transfer gadget is a spirit level, albeit sometime deliberately offset to some other reference.

A lathe in operation might not be much affected by whether it is "level", but discovering where it's bits are in relation to others, or the ups and downs of wear along it's ways, or whether there is twist, is most handily done with a spirit level. It _could_ be done by other means, but with a whole lot more trouble.  Of course twist is the enemy, and I see the level as the opposite, the friendly accurate tool to reveal it, and quantify it, and help us fix it!

The convenient starting point is just to level the ways, and it is here we discover that the whole thing is a bit bendy, and will twist if it's design load is not shared correctly between the supports. Over time, a support can relax. The sag may be imperceptible, but the force it delivers can disappear!


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## RJSakowski (Nov 28, 2021)

Any ex Navy machinists out there?  It would be interesting to see what the approved practice for setting up a lathe was.


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## woodchucker (Nov 28, 2021)

was there more than 30 seconds of video?
I don't do any social media, so I am a guest viewing. It ended after 30 seconds?


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## vtcnc (Nov 28, 2021)

woodchucker said:


> was there more than 30 seconds of video?
> I don't do any social media, so I am a guest viewing. It ended after 30 seconds?


There were two videos, 24 and 28 seconds, respectively. You can view them without restrictions.


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## rwm (Nov 28, 2021)

I often produce inaccurate parts when there is a full moon. I assume this is just a tidal effect on my machines.


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## woodchucker (Nov 28, 2021)

so what it says is the spirit size is different, meaning the reading of out of level is off. But level is not affected. the change is not one side or the other, only a non level item reads off. In other words if its .0005 it might be off by .001


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## vtcnc (Nov 28, 2021)

woodchucker said:


> so what it says is the spirit size is different, meaning the reading of out of level is off. But level is not affected. the change is not one side or the other, only a non level item reads off. In other words if its .0005 it might be off by .001


Right. Actual level is not affected if the reading is affected by temperature. What is affected is the action you take when a misreading occurs. So if it is off by .001 and actual is .0005, then you may shim the item out of level by .0005 if you make a misreading.


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