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  1. #1
    RC99's Avatar
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    Default Precision level required accuracy

    How would a 0.05mm/metre level accuracy go for use as a tool to aid in the refurbishment of machine tools...

    The usual recommended level, the Starrett #199 is 0.0005"/ft/graduation which is 8.6 seconds of arc..

    While the 0.05mm/metre is 10.3 seconds of arc..

    We often have the discussion of levels but as most of the members here are from the US the Starrett #199 is often the only level discussed but they are very rare items here on the second hand market and the suitability of levels of other accuracy is never discussed...

    Or indeed what accuracy levels are actually needed to level machine tools and to use for refurbishing machine tools..

  2. #2
    beckley23 is online now Titanium
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    The 0.05mm/meter level will be just fine for the application. One thing to consider is the surface of the level.
    The Starrett level has a flat bottom surface, as does my Scherr-Tumice, no grooves. Most of the imported levels I've seen, have grooves, which would cause me to exercise more caution in their use.
    Harry

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    The exact calibration of the level doesn't matter.

    The sensitivity is given in deflection per division, but there's no standard for the distance between the divisions.

    Any instrument accurate to about 10 arc seconds would be fine.

    I've seen some that are even more sensitive, around .0002"/ft.

    - Leigh
    .

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    RC99's Avatar
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    Thanks for the advice...

    I take it the 0.02mm/metre levels are designed for lab work in a temperature controlled room?

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    John Garner is offline Stainless
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    .RC. --

    You ask a question that I can't answer.

    What we in the US call a Master Precision Level (Starrett's Model 199Z is, by far, the most common and most widely known member of that genus, but other makers have included Berger Instrument, Lufkin, South Bend Lathe, Scherr-Tumico, Pratt & Whitney, Queen, Schulte, Taft-Peirce, Universal Boring Mill, and probably a couple dozen more) typically contains a vial in which the bubble will move 1/10 inch -- the distance between the vial graduations -- when the vial is tilted somewhere between 8 and 10 arcseconds. This requires that the inside of the vial be ground and polished to a radius somewhere between 215 feet and 172 feet.

    As you might expect, British level vials were traditionally graduated in 1/10 inch increments also.

    In contrast, modern European and Asian level vials are graduated in 2 millimeter increments. Having the bubble move 2 millimeters when the vial is tilted 0.05 millimeter per meter requires the vial curvature radius be 40 meters, roughly 131 feet.

    In my experience, the makers of precision level vials generally consider a vial to be usable if the measured sensitivity is within 10 percent of the nominal sensitivity. If European and Asian level instrument makers go along with the vial-makers +/- 10 percent tolerancing, a level instrument claiming 0.05 millimeter / meter sensitivity should actually range between 0.045 millimeter / meter and 0.055 millimeter / meter. Stated another way, the vial's radius of curvature should range between 36 meters (roughly 118 feet) and 44 meters (roughly 144 feet).

    So . . . the bubble in a standard US Master Precision Level will nominally move 1.6 times as far as the bubble in a 0.05 millimeter / meter level in response to identical tilts. At the extremes of vial sensitivities, the bubble in the standard US Master Precision Level could move as much as 1.8 times or as little as 1.2 times the distance the bubble in the 0.05 millimeter / meter level moves in response to identical tilts.

    Yes, the standard US Master Precision Level is a fair amount more sensitive than a level with a vial graduated at 0.05 millimeter / meter of tilt.

    Do you need the extra sensitivity when setting up or rebuilding machine tools? My best answer sounds awfully trite: You do if you do, and you don't if you don't.

    I'll make a suggestion, though. Go ahead and get started with a 0.05 millimeter / meter level, and when you get to the point that you know you need a better level, you can ask yourself if you can make do with a standard US Master Precision Level or if you need a 0.02 millimeter / meter level.

    John

  6. #6
    kevin johnson's Avatar
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    Quote Originally Posted by .RC. View Post
    Thanks for the advice...

    I take it the 0.02mm/metre levels are designed for lab work in a temperature controlled room?
    A Starrett 199 can make almost make you wish for a temp controlled lab if you have to move it and replace it very much in my experience.

    They are SENSITIVE.

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    Cool

    Quote Originally Posted by .RC. View Post
    I take it the 0.02mm/metre levels are designed for lab work in a temperature controlled room?
    Perhaps...

    But you'll seldom have the opportunity to set up a lathe in a temperature-controlled shop.

    Levels are fundamentally comparators, and as such they're self-calibrating. You calibrate the zero indication, then you adjust the machine to achieve zero.

    The calibration factor is only an indication of how close you need to be to that zero point.

    - Leigh

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    Pete F is online now Titanium
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    Quote Originally Posted by .RC. View Post
    We often have the discussion of levels but as most of the members here are from the US the Starrett #199 is often the only level discussed but they are very rare items here on the second hand market and the suitability of levels of other accuracy is never discussed...
    That's precisely the type of thing I find is worthwhile brining in from the US, either used through ebay or a cheap-arse rip off through one of the big cheap-arse rip off outlets I've bought 2 levels, one through ebay, one a rip-off. They're (relatively) low weight compared to their value here so I feel the cost of the freight represents a good investment.

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    RC99's Avatar
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    Quote Originally Posted by John Garner View Post
    Do you need the extra sensitivity when setting up or rebuilding machine tools?
    That is what I do not know.... I have come to the conclusion that a lot of people do things x way because grand dad did it that way and I am unsure if the same thought processes rings true of the use of the Starrett 199... Granddad used one so I will as well, which is all very well if Starrett 199's are common which they are not here...Hence my question about "other" levels of different accuracy ratings...

    Quote Originally Posted by The real Leigh View Post

    Levels are fundamentally comparators, and as such they're self-calibrating. You calibrate the zero indication, then you adjust the machine to achieve zero.

    The calibration factor is only an indication of how close you need to be to that zero point.

    - Leigh
    Yes I realise that when 99.9% of people use a precision level we are simply comparing one section to another and attempting to bring them into the same plane... The actual graduations are meaningless other then using them as reference points for the bubble.. It is the curvature of the vial that is the important bit...

  10. #10
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    If I use a 0,05 level on a lathe with a 20cm centerheight checking for twist
    1 deviation of that level represents a diameterdifference of 0.02mm
    So you can figure out of your own if it is accurate enough for you

    I liked to start with a 0,05 one and then move on to a 0.02mm/mtr

    Peter from Holland

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    Funnily enough, I've just moved all my machines to a new shed and had to re-level them. I used a stabila builders level to 'rough them out' when I put my Starret 199 on to finish them They where all spot on. Probably just dumb luck I suppose

  12. #12
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    Default How flat is your level?

    One other thing to check is how flat is your level, when I blued my Starret and spotted it, the contact points were at either end. Based on this I would recommend spotting and scraping if you want it to have 'truth' in your measurement
    David

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    Quote Originally Posted by beckley23 View Post
    One thing to consider is the surface of the level.
    The Starrett level has a flat bottom surface, as does my Scherr-Tumice, no grooves.
    As I understand it, this is NOT true.

    The "flat" bottom is in fact scraped "hollow", or concave along the length. The exact amount isn't given, but it may amount to a few tenths.

    Many other levels, like Lufkin, etc, were made with two pads at the ends and a distinct recessed and unfinished non-contact area in the middle. Not so Starrett.

    If you assume the level has a flat bottom, you may find that you get slightly varying results if using it on any surface significantly smaller than the length of the level base.

  14. #14
    DMF_TomB is offline Titanium
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    Default Level too sensitive

    a 0.02mm/m level is so sensitive that most of the time it will have bubble off scale or too far off center.
    .... most items sag if supported on ends. Even a 0.05mm/m level can pick up an object sagging in the center if supported on ends. put level off center on object and compare with level in center.
    ..... it is thought that modern level vials are internally ground with diamond plated wheels on cnc lathes. it probably is faster to grind the more sensitive level vial especially if someone is willing to pay more for it.
    ...... in China it is hard to find a precision level less sensitive than 0.02mm/m. When I asked for a 0.1mm/m or a 0.4mm/m level it was always answered with it can be ordered but is not stocked in the store. (A Starrett 98 level is close to 0.4mm/m)
    ....... the reason 99% of field machinist work is done with a 0.005" per ft(0.4mm/m) is it is easier to measure how much something is off or needs adjustment. you cannot easily measure if level is off scale. A Starrett 98 level can measure 0.001"/ft if careful and can easily measure 0.002"/ft. If you are setting or adjusting something to less than 0.001"/ft that would be around 4 full lines off on a 0.02mm/m level. (thats about the max that many levels can measure unless it is a big level).
    ....... most modern precision levels have a cross level vial. the level vial needs to be parallel in elevation (up and down tilt) AND azimuth (side to side adjustment). if main level vial is off sideways then when cross level vial is off a little, main vial can change 1 to 10 level line graduations. not many know that main level calibration requires not only setting so that it repeats when reversed but also that when level base vee is on a cylinder and cross level vial is deliberately put off center to watch if main level vial changes much.

    ........refer to Wyler web site
    BROCHURES + FLYERS / WYLER AG

    .......Wyler in my opinion is the leader in level technology. Most companies wish they had even 1/10 of what's in the Wyler catalog

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    Clive603 is offline Titanium
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    Quote Originally Posted by DMF_TomB View Post
    a 0.02mm/m level is so sensitive that most of the time it will have bubble off scale or too far off center.
    Agreed. There is a tendency to seek ultra precision, often at great inconvenience, without really thinking through the practical implications of what you are measuring or trying to measure. The 0.02 mm / m level Peterve mentions is getting into the realms of infra red optical interferometry. I spent enough years working in that area to appreciate things aren't as simple as they seem when you get that precise.

    My favourite tool for setting-up is the war surplus clinometer shown in the pictures. Maybe only a 30 seconds graduated vial but better than 5 seconds is easy to achieve. A clino is far handier to use than a master precision level, for starters you can keep the bubble in sight and there are a few handy dandy tricks as well. I figured that if one was good enough to help me get optical demonstrations aligned to silly levels of precision it was well up to the job of setting a machine tool.

    Clive
    Attached Thumbnails Attached Thumbnails clinometer-1.jpg   clinometer-2.jpg  

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    MikeJB is offline Aluminum
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    Quote Originally Posted by TonyOW31 View Post
    Funnily enough, I've just moved all my machines to a new shed and had to re-level them. I used a stabila builders level to 'rough them out' when I put my Starret 199 on to finish them They where all spot on. Probably just dumb luck I suppose
    Today I had exactly the same experience when levelling a surface grinder. Checking with a Hilger & Watts .05mm/m level no further adjustment was necessary after using the builder's level.

    Mike.

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