# Levels of precision



## Tin Falcon (May 24, 2013)

The thread free lathe reminded me of the fact that all levels are not created equal. 
I did some research and was surprised at the published data. 

A good carpenters level is good to .0005 in per inch this translates to .006  in/foot. max accuracy I was surprised at this claim as the starret 98 series is only rated to   .005 in per foot. 
a master precision level reads in .0005 in per foot. 

Use the best you can and remember a good level will always give the same reading when you turn the level 180 degrees.
Tin


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## enfieldbullet (May 24, 2013)

you can actually calibrate it with that 180 turn.

if the bubble is in the exact same spot after reversal that means it is calibrated. if it does not match you must tilt the vial or the base to adjust. on precision levels there are screws or something to allow adjustment.

you can use feeler gages to determine which side is lower and by how much. the aim here is to make the bubble stay on the same spot. remember to use the feeler gage on the same side of the level during adjustment.


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## /// (May 24, 2013)

Precision levels also have less curvature in the vial, making them more sensitive.
They also often have better scale markings making it easier to judge the bubbles position.
I have seen some cheap levels with at least 1/16" gap between the bubble and the markings at each end, useless.


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## dnalot (May 26, 2013)

OK I want a precision level but the price has put me off. Even the used ones on e-bay are pricey. So I bought the glass vial for a Starrett 12" ~ 15" level for $22 and I plan to make my own. I'm thinking I will make the body out of brass unless someone here thinks that's not a good idea. 

Mark T


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## enfieldbullet (May 26, 2013)

what is the vial's precision?

common practice for precision level is cast iron body, pin point scraped flat on the bottom.


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## Tin Falcon (May 26, 2013)

Not a lot of point in a precision vial if the bottom of the body is not near dead flat. 
Tin


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## dnalot (May 26, 2013)

The vial is  Starrett part number PT10524. It measures a little over 3.5" long. Perhaps steel or cast iron would be a better material. The surface would need to be honed to mate it perfectly to a surface table. 

Mark T


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## enfieldbullet (May 26, 2013)

you should if possible scrape it, best possible way of guaranteeing flatness.

cast iron scrapes well, steel not so much, and brass i believe is hard to scrape also although i have never scraped it, only engraved.


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## aarggh (May 26, 2013)

Would the glass vial itself be symmetrical enough? I recall Jans Ridders when making his engines found glass tubes didn't have enough tolerance to be used with graphite pistons, and had to get "precision" test tubes. If your tube is even slightly out at any point, the level will be out. Last year when I wanted to replace a couple of 1200mm levels, I quickly tested about 20 in store before I picked out the best that was there, I was stunned at the amount some were out.

cheers, Ian


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## enfieldbullet (May 26, 2013)

they're supposed to be supported at two points in both ends.

they're about cylindrical in the outside but barrel shaped on the inside, there's also that.

also, spreading those two points apart by making a base for the level increases it's ability to detect error. somewhat of an amplification effect.


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## aarggh (May 26, 2013)

What I meant was, the very minutest deviation from manufacturing will render it useless as a precision level, regardless of length. From the ones I've seen, the small individual glass vial levels are more for determining if things are more or less straight or plumb over a length or height. Any imperfections in the glass greater than 0.001" mean it's not a precision level? Have you run a micrometer over it, as if the outside isn't spot on, you can be sure the inside won't be. There's also the issue of machining a body for it, again, unless you can do it to 0.001" or less precision, the level will not be able to be turned around if there's any deviation to one side, as it will never read the same level when flipped. You'd need to build in some sort of very fine adjusting mechanism, and a lot of effort to get it to read right in the end.

cheers, Ian


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## enfieldbullet (May 26, 2013)

Ian,

i will have to disagree slightly.

the glass vial may be out of shape on the outside, because that part is not 'precision'. usually only the interior is ground to a slight barrel shape. and that grinding only ensures smooth dislocation of the bubble, otherwise it would dance around to much or jump from graduations to another.

the glass vial itself can't be used as a precision level because of the surface deviations you pointed out. however what i think he bought is the vial for a precision level, which now can be fitted on a base.

the precision needed for machining the base consists only of achieving a flat bottom surface. the vial is put on top and with adjusting screws you can make sure it shows true level.

what i meant to say, i guess, is that i think it can be done, and i don't think it would be too hard either. it would take some almost forgotten techniques but it won't take very expensive equipment.


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## Tin Falcon (May 26, 2013)

Options a good usa made master precision level new can cost several hundred dollars . Almost as much as many have in there budget to buy a late in the first place. 
so options a import one can be had for less than $100 .







master precision level on e -bay


There is another option buy a precision vial pre mounted in a tube made in USA and make your own base . a little more money and work but made in USA quality. 
For $ 90 you can get one that reads .0005 in/foot for a little more$102 you can get one that reads  by.0003 per foot .
Tin 

View attachment 4-6010_drawing.pdf


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## Davo J (May 27, 2013)

You can get a 8 inch level posted for $85 from CTC tools.
http://www.ctctools.biz/servlet/the-403/PRECISION-LEVELLING-OF-MACHINE/Detail

Dave


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## aarggh (May 27, 2013)

enfieldbullet said:


> Ian,
> 
> i will have to disagree slightly.
> 
> ...



I'm fine with that but my point was that unless the vial purchased was a high precision one already, which i'm fairly sure it wasn't, the inside as well as the outside are going to have imperfections whether you like it or not. And given the stated purpose was to make a precision level, no amount of adjusting the vial or the base it's fitted to, will completely remove any errors introduced by the variations of the imperfections. At best you'll get "close" or be able to use it in one direction, but as soon as you swing it around, any imperfections will magnify the error won't they?

My point is, you'll easily get it level, but given the OP wanted a precision level, how are you going to get a "precise" level, when the measuring implement isn't precision itself?

cheers, Ian


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## Tin Falcon (May 27, 2013)

There plastic vials made for run of the mill  carpenter levels. 
curved  glass tubes and precision ground glass vials. 
And lets not forget bulls eye levels  of various material and precision . The bulls eyes are used on balances and transits so we will not discuss those. 

do not be fooled  by the words machinist level or precision. without a Minute of angle or ten thousands per foot marking specs you really are guessing at what you get. 
take a look at the  Geier & Bluhm precision tuble level page many sizes and precision points to choose from. located in Troy NY USA.

sorry I thought i included this link in the last post.
tin


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## Tin Falcon (May 27, 2013)

CDCO tools has an 8"  10 second of arc master level for $58. the 12 in is $78

The level is marked .0003 per 10 inches. 
http://www.cdcotools.com/index.php
Tin falcon


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## jack620 (May 27, 2013)

Mark,
What are you going to use the level for?


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## Tin Falcon (May 27, 2013)

This PDF explains level sensitivity. The question is how much angle moves the bubble on division. The other difference between a precision level and a a carpenters level is markings. some levels have a pair of center marks only.

Tin 

View attachment Sensitivity%20-%20Tubular%20Levels.pdf


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## dnalot (May 27, 2013)

> Mark,
> What are you going to use the level for?



Its off subject, but you asked.

Another hobby of mine is building telescopes. Once built they need a very level surface to sit on to minimize the time it takes to setup the software for pointing, and to relieve the load on the tiny steppers that move the heavy device. 

This is my 12" dobson wide angle. 

The only machine used to built this was my homemade CNC router

Mark T


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## Tin Falcon (May 27, 2013)

if that is the case why not mount  a good bulls eye level to the base .
McMaster carr bulls eye level
then add leveling feet. 

http://www.mcmaster.com/#standard-leveling-mounts/=mxl2xb

tin


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## dnalot (May 27, 2013)

> if that is the case why not mount a good bulls eye level to the base .
> McMaster carr bulls eye level
> then add leveling feet.



That is what i have now. My mobile pylon is a 2" slab of concrete with adjustable feet and a bulls eye in the center. It gets me close but i still spend a considerable time taking readings from several stars to calibrate out the error. What works better if there is no wind is a Q-ball on a piece of plate glass. If you are right on the software can aim at and track a star. If you are not very precisely calibrated you have to hunt a little for your target. That's fine for stars, but i want to make a scope that's able to track satellites and they move fast so you don't have much time to be searching.


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## Tin Falcon (May 27, 2013)

What is the Minutes of angle rating on your current bulls eye. 

the 
2308A27 reads in 1 moa. 
tin


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## /// (May 27, 2013)

I use a bullseye for my Astrotrac portable pier and also for the portable pier I made for my EQ6pro.
Gets me close enough to level, then a quick polar align followed by a quick drift align, chuck the Newt Astrograph on and image for hours.
Never needed anything too precise. Maybe I just got lucky with this cheap bullseye :shrug:


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## dnalot (May 27, 2013)

It is about 4" in diameter and is labeled + or - 3 degrees.  I bought it from a surplus supply for a few bucks. It works good for star gazing as I have plenty of time to setup and plenty of time to acquire the target. My software is not sophisticated, mostly freeware and homeware. I got bored with stars and now I track satellites. Fixed ones are easy those that are moving are very difficult. my budget is very limited so I try to improvise as much as possible.


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## dnalot (May 27, 2013)

Forgot to press the send button and the photo didn't upload

Mark T


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## /// (May 27, 2013)

Have you had a go at the ISS yet? Quite a few people are getting good photo's of it these days and most are tracking by hand.


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## dnalot (May 27, 2013)

> Have you had a go at the ISS yet? Quite a few people are getting good photo's of it these days and most are tracking by hand.



That is a fast one, but its big and easy to find. With the small ones its not that there is something to "see" so much as the game of can you find it and can you track it. 

My main interest in scopes is not so much using them as it is building them. My Dobson is the only reflector scope I have made and the only computer driven one. Mostly I build refractor telescopes from 4" to 6" for terrestrial viewing. You can build very good scopes for very little money. Soon the theaters across america will be scraping their old projectors (they are going digital) and there will be a flood of very good surplus lenses.

Mark T


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## Tin Falcon (May 27, 2013)

back to the regularly  scheduled program. the master precision levels mention are intended for leveling and setting up precision machine tools such as lathes.  Although I do realize levels do have many applications. 
Tin


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## Davo J (May 27, 2013)

I posted this up on another forum a few years back, and thought it might help be of interest in this thread.

I have a few digital levels and angle gauges and over time have wondered how they compare to normal and precision machinist levels.
The standard type Stabila builders levels work out to have an accuracy of 0.75mm /per meter or 0.043 degrees

A machinist level like a Starrett No 98 is 0.005 in/foot or 0.42mm/meter per division which works out to be around  0.0239 degrees. 
The level divisions can be split by eye into 5 pretty easy which then works out to be around 0.00478 degrees or better.

The more sensitive levels like the Starrett No 199 or the cheaper alternatives from China are 0.0005 in/foot or 0.04mm/meter per division and they work out to be around 0.00240 degrees.
As above the divisions can be split into 5 pretty easy by eye which then works out to be around 0.00048 degrees or better.

So a digital level/angle gauge that has an accuracy of 0.1 degrees is over twice what a standard builders level is, and in my opinion is not really suited to machine work. It would need to have an accuracy (not resolution) of at least 0.01 degrees to be any good to use to set up a lathe etc. Even then it is a the high end of the scale because you can not spit 0.1 - 0.2 degrees etc, where a vial level can be split by eye between graduations.

Dave


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