Measuring inside dimensions, pockets etc
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    Default Measuring inside dimensions, pockets etc

    Hi all,

    I often need to get fairly accurate measurements of pockets and want to know what you think is the best tool for the job.

    Right now I'm working with a piece that has pockets that measure approximately 0.4" x 0.96" and my Mit digital caliper just isn't cutting it, I need more accuracy.


    I'm considering buying a Mit 145-193 "inside caliper" but want to know thoughts on it. Would a set of telescoping gauges be a better investment?


    716jpnvf8ll._sl1500_.jpg

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    Gage pins and/or a stack of gage blocks.

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    Telescoping gauges are best for measuring bores. They need the curved surface to get them aligned.

    What's the environment? Are you trying to measure in the machine or on a surface plate?

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    For that size of a pocket, I would agree on the gage blocks.

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    Quote Originally Posted by mTeryk View Post
    Telescoping gauges are best for measuring bores. They need the curved surface to get them aligned.

    What's the environment? Are you trying to measure in the machine or on a surface plate?
    Sometimes on the machine, but more often than not I'm measuring at my desk while drawing in CAD.

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    For rectangular pockets I like adjustable parallels. They sort of average out the surface's bumps and reflect what the max size of the mating part can be.

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    Quote Originally Posted by cj133 View Post
    Hi all,

    I often need to get fairly accurate measurements of pockets and want to know what you think is the best tool for the job.

    Right now I'm working with a piece that has pockets that measure approximately 0.4" x 0.96" and my Mit digital caliper just isn't cutting it, I need more accuracy.


    I'm considering buying a Mit 145-193 "inside caliper" but want to know thoughts on it. Would a set of telescoping gauges be a better investment?

    716jpnvf8ll._sl1500_.jpg
    Maybe just me but what to you mean by "pocket"?

    1. Is it a recess/groove in a hole or .....?

    2. If it is in a hole what's the min diameter?

    3. If an inside micrometer isn't accurate enough what kind of accuracy are you looking for?

    Personally I can't see telescoping gauges beating a micrometer for accuracy.

    A sketch/drawing of what you want to measure would help - me at least

    With what I have in mind maybe your Mitutoyo caliper can do the job.

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    Quote Originally Posted by Gordon B. Clarke View Post
    Maybe just me but what to you mean by "pocket"?

    1. Is it a recess/groove in a hole or .....?

    2. If it is in a hole what's the min diameter?

    3. If an inside micrometer isn't accurate enough what kind of accuracy are you looking for?

    Personally I can't see telescoping gauges beating a micrometer for accuracy.

    A sketch/drawing of what you want to measure would help - me at least

    With what I have in mind maybe your Mitutoyo caliper can do the job.
    I'm asking if an inside micrometer is a good buy, basically.
    Right now I'm using a Mit digital caliper, and it's not accurate enough.

    I can't give a drawing as there's way too many times I'm trying to measure the ID of random things. Pockets, holes, grooves etc.


    I just wanted some input before burning $220 on the inside micrometer.

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    What is the depth of the pocket?

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    Quote Originally Posted by cj133 View Post

    I just wanted some input before burning $220 on the inside micrometer.
    I would by the cheaper version like a Fowler or similar. Those types of mics are just not that accurate by design. I have the .2-1.2 version like you pictured and the 1-2. I'm not a big fan of either but I use the 1-2 a lot more than the .2-1.2 because it can reach down inside. If the pocket is bell mouthed the mic you have picture will give you false readings.

    They work but if I need to check something more accurate than my calipers can achieve I usually grab something other than these.

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    For the measurement of most irregular shapes I am using a toolmaker's microscope. I have a large "Leitz" as well as a smaller unit.

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    If this is just for in process check before you validate off the machine with a real piece of inspection equipment use a 3d indicator in your machine spindle

    https://www.haimer-usa.com/products/...3d-sensor.html

    You could use a height gage off the machine on a surface plate

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    Quote Originally Posted by cj133 View Post
    I'm asking if an inside micrometer is a good buy, basically.
    Right now I'm using a Mit digital caliper, and it's not accurate enough.

    I can't give a drawing as there's way too many times I'm trying to measure the ID of random things. Pockets, holes, grooves etc.

    I just wanted some input before burning $220 on the inside micrometer.
    I can't think of a single instrument that can do all the things you want to do.

    You've mentioned "accuracy" more than once but how accurately do you need to be able to measure? "Pockets, holes, grooves etc." don't usually have the same grade of tolerance.

    IMO you're asking an unanswerable question as can be seen by all the questions you're getting. We need more information to give good advice.

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    Quote Originally Posted by Gordon B. Clarke View Post
    I can't think of a single instrument that can do all the things you want to do.

    You've mentioned "accuracy" more than once but how accurately do you need to be able to measure? "Pockets, holes, grooves etc." don't usually have the same grade of tolerance.

    IMO you're asking an unanswerable question as can be seen by all the questions you're getting. We need more information to give good advice.


    This is possible.
    Let's start with what I'm currently working on. Dimensions are all in inches.

    What would be the best way to measure the pockets in this at your bench? +- 0.001"

    sample1.jpg

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    Gage pins. Since a set would cost much more than $220 I would buy a decent gage block set. That would be your most accurate and universal.

    99/100 times the length will not need to be +-.001 critical so just hit that with the calipers you already own.

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    Inside micrometers like the one you pictured will do the job. It may take a bit of practice to get consistent with them, but if you are in your office measuring parts to duplicate in drawings, they will be more handy to use than a big set of gage blocks and pins

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    Quote Originally Posted by cj133 View Post
    This is possible.
    Let's start with what I'm currently working on. Dimensions are all in inches.

    What would be the best way to measure the pockets in this at your bench? +- 0.001"

    sample1.jpg
    OK thanks. As you want to measure within ±0.001" then your tolerance is ±0.01"?

    What I'd do is use/buy some cheap calipers (vernier or digital) and use them as Go NoGo gauges.

    Set the internal measuring jaws with a good micrometer to the max and min on each size you wish to measure and lock the calipers in that position. You'd be getting the same result as if using a telescope gauge.

    OK Go NoGo isn't measuring so what you also could do is use a caliper, make contact with the dimension, lock the caliper and then measure with a good micrometer. IOW the same as what you'd do with telescope gauges.

    Not perfect but probably good enough to buy you the time to find what it is you are looking for. I'll be surprised if you can't measure to within ±0.001".

    As I've already mentioned - there is no single instrument that can do everything you want to do. Even my suggestion requires two - a caliper and a micrometer.

    I've got an idea that'll make measurement easy and that you can easily make yourself so I'll try and post a picture tomorrow.

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    well holy hell, if +-.001 is good enough there isn't any reason I can think of you shouldn't get that with a decent Mitutoyo (or any quality brand) caliper.

    good technique is of corse required, practice inside measuring using a good micrometer as a "gap gauge" if it isn't fairly repeatable, toss it, or get a new operator!


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    Gage pins and gage blocks to measure the slot length.

    4 place decimal on a radius? How can you do this without already having good metrology dept.

    Dave

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    Pockets those sizes I like to use adjustable parallels and take the measurement directly off those, If I'm cutting the whole part I also measure flange thicknesses and calculate the missing dimensions from the over all part measurements. I really don't know if you're splitting tenths or running plus or minus .002"
    Dan

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