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ID micrometer, is it worth buying one?

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  • Mcgyver
    replied
    Originally posted by RLWP View Post
    Taydin, haven't you bought a bore comparator? I have a Starrett device very similar, used for measuring the deviation in the diameter of a cylinder. Typical use is to see if a car engine needs a rebore.

    It's brilliant at showing up differences, next to useless for measuring the actual size
    these are the most accurate way to measure a bore, at least via what might appear in a home shop. The sweep is centred, the reading noted then compared with a micrometer (in a perfect world we'd all have ring sets) . You are right, its comparative, but is nonetheless used to get very accurate measurements by comparing to a 10ths micrometer or gauge block stack. They are commonly available with 10ths or micron indicators and are reliable and repeatable.

    Of course not everyone needs one, but my point is not only are for measurement of actual size as well as out of round conditiions and they are probably the most accurate way to go about it short of some uber expensive coordinated measuring system. In most cases telescoping gauges or small hole gauges are good enough but if making very precise fits for roller element bearings they are the tool to use imo
    Last edited by Mcgyver; 02-01-2013, 04:15 PM.

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  • Timleech
    replied
    Originally posted by RLWP View Post
    It wouldn't have been my choice for that job Tim

    Richard
    Probably not mine either, too much messing about, but can be used for pretty accurate bore measurement as well as comparison.

    Tim

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  • RLWP
    replied
    It wouldn't have been my choice for that job Tim

    Richard

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  • Timleech
    replied
    Originally posted by RLWP View Post
    Taydin, haven't you bought a bore comparator? I have a Starrett device very similar, used for measuring the deviation in the diameter of a cylinder. Typical use is to see if a car engine needs a rebore.

    It's brilliant at showing up differences, next to useless for measuring the actual size

    Richard
    Set an outside micrometer to the size you want, then adjust the bore comparator to read zero at that size. Fiddly but not all that difficult if you have three or four hands I think there are special jigs for doing it if it's something you do all the time.

    Tim

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  • RLWP
    replied
    Taydin, haven't you bought a bore comparator? I have a Starrett device very similar, used for measuring the deviation in the diameter of a cylinder. Typical use is to see if a car engine needs a rebore.

    It's brilliant at showing up differences, next to useless for measuring the actual size

    Richard

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  • SGW
    replied
    If 'twere me I'd probably bore to a reasonable slip fit and apply Loctite 641 Retainer.

    http://www.useloctite.com/filephotos...ions_Guide.pdf

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  • taydin
    replied
    Then took some time to RTFM (yes, this one had a manual in it!) and finally tried measuring the bearing seat I made. Quickly realized that one of the anvils isn't touching the bore (picture below). Had to insert spacers to the front anvil to correct that. Then I took my 50 - 75 micrometer and fixed it to 52mm. Then I worked on zeroing the indicator. This is really the most tricky part. Finding the minimum really takes some skill. After coming close to zero with an uncertainty of +/- 0.02mm, I tried taking the actual measurement. But the actual measurement looks off by 0.55mm ! Something is wrong...

    Last edited by taydin; 02-01-2013, 08:12 AM.

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  • taydin
    replied
    For some reason, they have put a plastic shell around the indicator. Had to take that off, otherwise the indicator doesn't go into the long tube:

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  • taydin
    replied
    Ok, got my new, shiny dial bore gauge This one is a 50 - 160mm model. Nice range, I liked that ...

    Last edited by taydin; 02-01-2013, 08:10 AM.

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  • taydin
    replied
    Originally posted by RLWP View Post
    Being ludicrous for a moment, If the bore were 1" diameter, and the calipers had a width of 1/8", the error would be .004" on the diameter

    I don't have any calipers anywhere near as crude as that, or measure bores that small with them

    I'm beginning to realise I am a dinosaur. I use hand ground HSS tools to skim fractions of a thou out of bores instead of tipped tools. I use calipers by feel to measure when boring for bearings. I look for solutions around me rather than in a tool catalogue. I don't have digital readouts or air gauges. It's a wonder I can make anything at all

    Richard
    I apologize if my comment about the go/nogo gauge came across like "ah, I know that won't work". My comment was rather meant as a question, trying to understand how it makes things easier.

    And, you are not a dinosaur... My dad is retired boring mill operator, and worked for 30 years at a German factory. He was building critical parts, for nuclear reactors and such, and he never used an edge finder. He also was a traditional machinist with traditional methods that work.

    I am one of the least experienced/knowledgeable members here, so I haven't argued about technical issues with anyone here and I won't.

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  • taydin
    replied
    Originally posted by EVguru View Post
    But there are also these.
    This is the type that I had in mind when I opened this topic.

    But thank you for summarizing all possibilities...

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  • EVguru
    replied
    It seems to me that there is some confusion here as to exactly which measuring tools are being talked about.

    To some, this is an internal micrometer.


    But there are also these.


    A spring joint caliper would be a traditional tool for bore measurement.


    For many a slide caliper (whether Vernier, dial, or Digital) would be the first tool of choice.

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  • Timleech
    replied
    Originally posted by RLWP View Post
    Being ludicrous for a moment, If the bore were 1" diameter, and the calipers had a width of 1/8", the error would be .004" on the diameter

    I don't have any calipers anywhere near as crude as that, or measure bores that small with them

    I'm beginning to realise I am a dinosaur. I use hand ground HSS tools to skim fractions of a thou out of bores instead of tipped tools. I use calipers by feel to measure when boring for bearings. I look for solutions around me rather than in a tool catalogue. I don't have digital readouts or air gauges. It's a wonder I can make anything at all

    Richard
    I sense some confusion between different posters over different types of calipers, though I confess I haven't read every word of every post.
    Surely 'inside calipers' have radiused tips, so 'width of flat' shouldn't come into it.
    Verynear and digital calipers will have a very narrow flat on the inside jaws, but they're really only useful for rough & ready inside measurement anyway (IMO)

    Personally I've never really got on well with inside micrometers, & up to a certain size I'll get more reliable results with telescoping gauges and an outside mic.

    Richard, I can recommend DROs, one technical advance which is well worthwhile

    Tim

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  • RLWP
    replied
    Being ludicrous for a moment, If the bore were 1" diameter, and the calipers had a width of 1/8", the error would be .004" on the diameter

    I don't have any calipers anywhere near as crude as that, or measure bores that small with them

    I'm beginning to realise I am a dinosaur. I use hand ground HSS tools to skim fractions of a thou out of bores instead of tipped tools. I use calipers by feel to measure when boring for bearings. I look for solutions around me rather than in a tool catalogue. I don't have digital readouts or air gauges. It's a wonder I can make anything at all

    Richard

    Leave a comment:


  • Jaakko Fagerlund
    replied
    Originally posted by MaxxLagg View Post
    I disagree. If you're trying to hold +/- .0002 on a bore diameter using calipers like you would a telescoping gage they aren't going to achieve that. First, you're never going to get the same, repeatable sweep of the maximum ID of the bore as you can with telescoping gages. Secondly, take a close look at the faces of the jaws on the inside measuring jaws. I have four calipers sitting here in front of me of various makes, sizes and styles. That, albeit small, flat that each jaw has is going to prevent you from fully measuring the ID of the bore. By how much? Well, mathematically you could determine this amount by calculating the height of the chord that results by the width of the flat and multiplying this product by two and adding it to your measurement. But to do this you would need to know the radius of the bore to input into the formula for figuring chord height, which you don't.
    So what you are saying is that you have never even used such a technique, because you say it doesn't work? It works exactly the same as telescoping gage: transfering the ID measuremet to OD measurement, only the device to do so is different.

    And if the jaws of a caliper can't be measured according to you, then what exactly does contact the bore? Because you are in a sense saying that the jaws are not touching the bore. Newsflash: I didn't say to measure over the flats.

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