Haven’t been around Breaktime in awhile since I moved. The only internet available at our new location was the slowest dialup imaginable. Now that I’m surfing with satellite broadband I’m back in the game. Surprised to see I had to re-register but also happy to see that after a couple years, many of the same ole’ regulars are still around.
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Now to my question… Was showing a rookie how to check a level to make sure it still gives good readings. You know the old method of taking a reading then rotating it 180 degrees and looking for any discrepancies. Then I got a question about shouldn’t it be turned over (flipped) and checked too?
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Had to ponder that one for a moment. My conclusion was unless one edge of the level had a defect, discrepancies should be the same with both sides of the level.
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Thoughts?
sdr1 (aka Scott R)
Replies
Each vial should be checked.
The stick itself doesn't suddenly become trapesoidal, the vials shift slightly.
SamT
So much of the success of a company is not determined by degrees but temperature. gb93433 83537.46
Better than see if it reads off the same in both directions shim up the low side until the bubble is exactly centered. Then flip it.
Much easier to see a small error that way.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Discrepancies should be the same after the "flip", just reversed. If the vial is out of parallel in relationship to the body of the level it is out no matter which way you view it.
Amazing how many levels get sold that aren't accurate!!
The reason I prefer the "cheap" bubble sticks with 4 little screws holding the vials in.
Adjustable.
I'ld much rather have to check adjust once a week than to have one forever out of true.
Find a blank wall and carefully set two nails dead level as a stick holder. Storing all my levels on pairs of these lets me see at a glance if at least one bubble is true or not. Adding a verticle line or fence right there makes a Calibration center.SamT
So much of the success of a company is not determined by degrees but temperature. gb93433 83537.46
I just buy Stabilia.. never had one go out of level or plumb yet.
Edited 1/17/2007 5:10 pm ET by dovetail97128
When I worked in a lumber yard we had a salesman come through and took a Stabila level and slammed it hard on the concrete floor and it remained level. I have had MD levels with the four screws and eventually they always go out of adjustment and have to be readjusted especially in hot weather.
Piffin screws are perfect for the leveling job.
blue"...if you just do what you think is best testing those limits... it's pretty easy to find exactly where the line is...."
From the best of TauntonU.
Blue,
A water level has been used for centuries.
Chuck Slive, work, build, ...better with wood
Dovetail, that’s exactly what I thought.
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Upon further thought I suppose flipping to do a check both sides would be a good idea for mahogany mason levels. The brass edge pieces tend to get screwed up. In fact I own one, the level is only good on one side.
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Thanks for all the input!
I buy Masterlevels that are adjustable. Some guys here don't like them, but I love 'em. It's easy to assess and adjust them. However, I only ever use one side. The Master horizontal vials are on the edge, with cut-outs, so this is always up. The vials are rounded too. Therefore, the level is made to be used only one way. On the vertical, it could be used either way, but I have noticed slight discrepencies, so I always use the same side I adjusted. Make sense?
How accurate is accurate? I have wondered about this. I know they say the human eye is pretty good of very good at centering things, but how good is that? Any one know? What is the likely range of error over say 50 feet using a four foot level, for example.
Stabilia levels I believe all have the same accuracy range. Mine has it printed right on the level..Guaranteed as long as the frame is not bent.
Verticle .075mm/m or .043"/39"
Horizontle .05mm/m or .029"/39"
The issue with your question is how do you create the straight line extending 50'. If you extended a straight line for 50' the margin of error would be 15.24 x the .043" =.65532" (5/8")
Good quality Builders Levels which use a sight glass vial and telescope easily achieve 1/8" at 100'
I have a machinsts level that I inherited from my father that has a 2" long vial in it. It is a Starrett and I would bet it is even more accurate than the Stabilias.
Starrett lists that level as having a "100 second accuracy". I don't know how to translate that into a percent of inches though.
one thirtysixth of a degree?
.028*?SamT
Guys that don't do things correctly the first time.....then argue that they did nothing wrong.....if made to agree to fix the problem, rarely put the time and effort into truely doing it properly. they'll just look for the quickest fix to appease you and get their money. JDRHI <!----><!----> 84310.51
Is that a statement or a question? ;-)
I actually would appreciate someone among the math whizzes here to work it out and tell me the level of accuracy on the old Starrett. All I know is that it shows the bookcase that it lives in to not be level!!http://catalog.starrett.com/catalog/catalog/groupf.asp?GrpTab=Feature&GroupID=487
Edited 1/18/2007 7:29 pm ET by dovetail97128
this is from : http://www.1728.com/trig.htm
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Do ya think that's right? .05' rise over 100 run. That'ld be 5/8" error in in 100'SamT
Guys that don't do things correctly the first time.....then argue that they did nothing wrong.....if made to agree to fix the problem, rarely put the time and effort into truely doing it properly. they'll just look for the quickest fix to appease you and get their money. JDRHI <!----><!----> 84310.51
Sam ,
I honestly don't know. I am brain dead at working angles out with math.
But if every degree of angle has 60 minutes to it, and every minute of angle has 60 seconds to it. Then each second = 1/3600 of a degree.
So that would mean that it's accuracy is to 1.6666 minutes of a degree.
Starrett list the level as having "100 second " accuracy.
The level is 12" long.Edit: Sam I went back to the link I posted and at the bottom it says
""The 6" through 18" (150-450 mm) main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42 mm per meter). There are five, six, or seven lines on each side of the bubble, depending on the base length.""
So if we call the 90 seconds 100 seconds for sake of discussion then accuracy is somewheres near .005/ft. at 100 ft that = 7/64ths.
Course I may have this all wrong as well. Need one of those friendly guys who worked out the rafter pitch problem with a computer to tell me.Maybe I will start a thread at general discussion and see if I get any takers on this.
Edited 1/18/2007 8:52 pm ET by dovetail97128
""Do ya think that's right? .05' rise over 100 run. That'ld be 5/8" error in in 100'""
Must be someone else came up with 9.3 / 16th.'s
I will never doubt your wisdom again.!! Just calculated that the Starrett is nearly twice as accurate as the Stabilia and is at least 70 yrs. old.
Edited 1/18/2007 9:36 pm ET by dovetail97128
100 seconds = (1 degree / 60 minutes) x (1 minute / 60 seconds) x 100 seconds
= 0.02777778100 feet = 1200 inches100 seconds in 1200 inches is1200 Sin 0.02777778 = 0.58177692 inches
dove, my point is that all bubble levels are only as good as your ability to read and declare the bubble equal distance between the lines in the viles! How good is the human eye in this task? I know that they say the eye is pretty, or very good at centering things, but how good is that.
In this regard, a plumb bob is superior to levels for plumbing a wall for example. A plumb bob relies on no judgement call of the eye. Now, we are talking about framing, and many people call it "ROUGH" framing, so I am not talking about any pratical difference. Just interesting in the discussion. However, I suppose if you are plumbing a 15 of 20 foot wall, a level could introduce a significant level of error.
Ahh, I understand your question. I have been told , but can't remember what the human eye is capable of discerning.
I have seen a lot of "leveled" walls that had discernable error just using my eye to check them. Plumb bobs don't lie.
dove, not all eyes are equal. I actually think my eye is pretty good as well. I recall going to a sight with a structural engineer and he was wondering around and around and around. I could not understand why he did not immediately go straight to the floor. In my eye the floor was obviously not flat. It sloped off to the back of the lot. Finally I pointed it out to the guy. He looked at it and said, "looks ok to me". I asked the guy to humor me, and get his level. Sure enough, the floor sloped off about 3/4" over 20 feet. As a result we focused on the refoundation and found that it has slide down the hill some amount. Not a good thing.
As for levels it seems to me, if you are off by a nanometer in centering the bubble in the level and the bubble is less than 1/4" long over 48 inches you would be off something in the neighborhood of 200 nanometers. Naturally bubble levels have been used for a very long time by millions of people and builders so they are fine. Again, just curious as to the accuracy which is generally obtained with their use.
Higher accuracy vials have a larger radius, thus, a slight difference in tilt moves the bubble further.
A quick lesson in trig for the math challenged. Using terms that humans understand, not the opposite hypotonuse stuff that confuses most people.
the tangent of an angle is the rise/run.
the sine of an angle is rise/slope
the cosine of an angle is run/slope.
Draw a triangle and lable it that way, use it a few times and you will have it memorized. I've taught a lot of guys basic trig this way.
100-seconds is about 0.6-inches at 100-feet.
1-minute of angle is 1/60th of a degree
1-second of angle is 1/60th of a minute
1-minute of angle is 1-inch at a hundred yards.
A variation on the nail trick is to use screws to adjust one side dead nuts then flip the level around to check the other three plumb options.
When laying out long level lines it's best to rotate the level to cancel out any discrepancies.