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drsquat
10-24-2003, 11:23 PM
yea i know, the first mistake was buying this machine level from grizzly. armed with a granite slab i checked it for error. yep i was off. so now i am trying to correct that. so now i have a level i dont trust even when i do , IF in fact, i get the error out of it. only armed with the granite slab again from grizzly how in the heck am i to know that when the bubble is centered that it is level?

wierdscience
10-25-2003, 12:04 AM
Simple,turn the level end for end,if you get one reading as being level when you turn the level end for end you should get the exact same reading,or am I missing something?

drsquat
10-25-2003, 12:10 AM
ok but what can i do to ensure that the bubble shows level and the body of the level is also level. is there another method to use other than finding a certified level surface, say.... at a machine shop. yea i know how to check to see if it has error but i dont know how to guarantee that its actually level.

Joel
10-25-2003, 01:09 AM
That's what a level does, as Weird pretty much points out.
If the bubble reads dead center on a flat surface, no matter which way you turn the level, that surface IS level. If it reads slightly to one side when you turn it either way (reads exactly the same off level) your level is good, but your surface is off level by the amount shown. Guaranteed.

darryl
10-25-2003, 02:07 AM
If there is an adjustment for the bubble, follow the procedure of turning it end for end, and adjust until the bubble reads centered within the lines either way. If this cannot be achieved, the surface you're truing it on isn't level, so you'll have to adjust that. When you can center the bubble the same when you turn end for end, the level is adjusted, and the surface you're truing it on is level, as well.

[This message has been edited by darryl (edited 10-25-2003).]

Evan
10-25-2003, 02:13 AM
Darryl,

The surface might not be exactly perpendicular to the local gravitational normal. If the level reads the same, not necessarily centered between the lines, but the same when reversed, then it is correct.
--------------
Midstream editosis strikes again, eh?

[This message has been edited by Evan (edited 10-25-2003).]

JCHannum
10-25-2003, 08:34 AM
What Darryl is describing is a method to adjust level and surface simultaneously, and is correct. If you use a relatively level surface, and just turn the level, you will pretty well zero the level to your best ability to estimate and duplicate the error in reading in each direction. If you adjust both until there is no movement in the bubble, the level is zeroed out.
It works much like centering something in a 4 jaw with a wiggler. When done, both are dead on.

Oso
10-25-2003, 11:10 AM
There was a posting on another forum about Grizzly levels.

That guy found that the bottom of his was concave, and sat on only three out of four of the corners when put on a granite flat.

He sent it back, they credited him and paid shipping, if I recall correctly.

My advice would be to send it back and get credit, and then buy a real one.

They might have sold you the one he returned..... http://bbs.homeshopmachinist.net//biggrin.gif

Forrest Addy
10-25-2003, 11:27 AM
Levels are self-checking. All you need to calibrate a level is a flat stable surface that's approximately level. The surface may have a slight slope but at 90 degrees to the slope and in plane with the surface will be a line which is level. You can find the line by checking with the level, rotating it while looking for a consistant reversal error. Then you can fix the line by laying a heavy parallel on the surface.

Procede with the calibration with a glad heart. A precision level can be calibrated in an open shop to as great a degree of precision as one calibrated in a controlled cal lab. Just be sure that handling the level doesn't affect the calibration by injection of body heat.

As for cheap levels whose reference face may be out of flat, you're a machinist, aren't you? Get out the blue, the granite flat, a slip stone, and a scraper and make it flat.

[This message has been edited by Forrest Addy (edited 10-25-2003).]

darryl
10-25-2003, 03:24 PM
Midstream editosis, I sure hope there's a cure for that. Anyway, you're right, Evan, just turning the level and seeing the bubble offset the same ammount, in the same direction, says that the level is accurate. The surface you test it on doesn't have to be level.
Out of the blue, I got a phone call from a guy who wanted to get rid of some 'junk' that had been left hanging around his barn. Lots of these things were tools, one of which was a level. This one had an adjustable bubble with a pointer which indicated over a range of + or - 5 degrees. He wouldn't part with it.
Now for a little poststream edit, re the gravitational norm. Is that why some rivers can flow two directions at once?

[This message has been edited by darryl (edited 10-25-2003).]

drsquat
10-25-2003, 04:47 PM
thank you guys your info has relieved a lot of frustration. now on to my 12x36 atlas with a little more confidence

wierdscience
10-25-2003, 08:41 PM
Midstream editosis,penicillin I think http://bbs.homeshopmachinist.net//biggrin.gif

Evan
10-25-2003, 11:54 PM
Gravitational normal doesn't always point to the center of the earth. It depends on what masses are nearby, like, say, Mt. Everest. Seriously, they look for ore bodies with gravitometers towed behind a plane so the gravity of the plane doesn't affect it so much.

darryl
10-26-2003, 12:30 AM
Now I'm thinking again (dangerous?) Isn't there a road somewhere that slants just a bit, and the gravitational norm is off, so a car can actually roll uphill on it- I bet they didn't use a level to see if it's uphill or not. What device would one use to check the absolute 'levelness', where gravity can't be used, a gyrolevel?

Evan
10-26-2003, 01:31 AM
Gravity is as gravity does. That is the only "level" there is.

Joel
10-26-2003, 12:03 PM
In other words, anything that affected the level, would also affect the car. The level is where the term "uphill" would have to come from. You have to watch Evan sometimes, http://bbs.homeshopmachinist.net//smile.gif his scientific mind points out that most things are not really absolute. Effects such as this are generally very small, for example, You know that you age more slowly on top of a mountain, or if you are driving?
I tried to straighten a picture on the space station the other day, now that was tough. Every direction was level in relation to something!

darryl
10-27-2003, 03:46 PM
Oh, man, I guess an interior decorator would go insane aboard the space station.

drsquat
10-27-2003, 04:16 PM
now i understand the concept of adjusting a level and now i have it properly adjusted
thanks all
and a note of advise...... never accept lemonade from a urologist

Evan
10-27-2003, 04:19 PM
Joel,

While on top of a mountain your absolute velocity is higher so there is a slight slowdown of time due to Lorenz Contraction. BUT you are also further out of the gravity well so time dialation is reduced in direct proportion. I suspect the net result= zero difference, depending on rotational period.

I like the topic gravity because I know just as much about how it works as the most educated physicist in the world. Which is exactly squat. It resists all attempts to explain how it fits into the big picture. Einstein was able to describe its properties and characteristics but not the mechanism. It must be really frustrating working in quantum mechanics and knowing that no matter how well the theory describes the properties of matter there is one property that it does not. The best explanation is simply that gravity sucks.



[This message has been edited by Evan (edited 10-28-2003).]