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    Quote Originally Posted by DMF_TomB View Post
    .
    Tram gages either mic or indicator type have been used to measure inside to inside or outside to outside dimensions compared to reference rod or gage block or ring gage for hundreds of years. originally used to set railroad tracks parallel. and printing press rollers parallel. the base is often wide enough to assist in squaring it
    .
    the swivel connecting type can be a curve that is go around a roller in between 2 other rollers. hard to describe. been used by millwrights for centuries although early ones just used a fine threaded screw instead of a micrometer or indicator
    .
    yes thats a trammel point end for fine adjustment on the one end. trammel points were adapted for Tram gages for centuries. obviously if 5 foot long repeatability is not less than .001"
    .
    most millwrights have made a few Tram gages. i have made dozen of varies types all different sizes. Telecoping type is often adapted from a snow brush. that is a tripod leg or something else using telescoping tubing that locks to different lengths. i have also adapted pipe tubing compression fittings to not stay permanently crimped on tubing when unlocked. most experienced millwrights can go to any hardware store in any city in the world and in 10 minutes adapt something to have a Tram gage
    Thanks for taking the time to explain. I think i get the majority of what you are saying.

    Enough gage blocks to make a reference that long sounds pretty expensive. I assume reference rods is an equivalent term for micrometer standard? And you would need to stack a few together for the very long measurements? Probably best done in an aluminum angle?

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    Quote Originally Posted by Hillside Fab View Post
    Thanks for taking the time to explain. I think i get the majority of what you are saying.

    Enough gage blocks to make a reference that long sounds pretty expensive. I assume reference rods is an equivalent term for micrometer standard? And you would need to stack a few together for the very long measurements? Probably best done in an aluminum angle?
    when checking that size reference blocks could and will give you false readings even on a mic. just because of pressure.
    you use good startett/webber(or equal) gage blocks of the size your measuring wring them and stack them properly.
    running big parts cost money to do it correctly, if you dont you scrapped huge amounts of money because of using a sub par method of inspection.

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    Quote Originally Posted by DMF_TomB View Post
    .
    Tram gages either mic or indicator type have been used to measure inside to inside or outside to outside dimensions compared to reference rod or gage block or ring gage for hundreds of years. originally used to set railroad tracks parallel. and printing press rollers parallel. the base is often wide enough to assist in squaring it
    .
    the swivel connecting type can be a curve that is go around a roller in between 2 other rollers. hard to describe. been used by millwrights for centuries although early ones just used a fine threaded screw instead of a micrometer or indicator
    .
    yes thats a trammel point end for fine adjustment on the one end. trammel points were adapted for Tram gages for centuries. obviously if 5 foot long repeatability is not less than .001"
    .
    most millwrights have made a few Tram gages. i have made dozen of varies types all different sizes. Telecoping type is often adapted from a snow brush. that is a tripod leg or something else using telescoping tubing that locks to different lengths. i have also adapted pipe tubing compression fittings to not stay permanently crimped on tubing when unlocked. most experienced millwrights can go to any hardware store in any city in the world and in 10 minutes adapt something to have a Tram gage
    Pic didn't come thru I guess, but no way I would trust that to +/-.005" (I think that is what Ox was looking for?)!!. Maybe... maybe +/-.010"....

    Even then, "I" would have to set it up and plan out how I was using it to get the best possible scenario.

    (bold part) really? ya don't say...

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    Quote Originally Posted by Delw View Post
    when checking that size reference blocks could and will give you false readings even on a mic. just because of pressure.
    you use good startett/webber(or equal) gage blocks of the size your measuring wring them and stack them properly.
    running big parts cost money to do it correctly, if you dont you scrapped huge amounts of money because of using a sub par method of inspection.
    I am not arguing. How much would a 20", 10", and 6" (or 5" so you could 'dial it in with some smaller ones) cost? Ouch!

    20" Square Steel Gage Block 86277506 - MSC

    Then the nightmare (IMO, maybe this is common in some places?) of storing and calibrating it. Maybe my thinking is wrong, but the longer the block, the more temps are going to affect it, and handling it...

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    Maybe of interest to some but still smaller than what Ox is interested in.

    din-standards.jpg

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    Our shop used 6" I think we had a few 8"
    it gets real expensive when you had 4 machines running 2-3 different muellers bars at the same time. after I had left in 94 they ended up buying a huge cmm.
    we had an older cordax one but it sucked.

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    Quote Originally Posted by Delw View Post
    when checking that size reference blocks could and will give you false readings even on a mic. just because of pressure.
    you use good startett/webber(or equal) gage blocks of the size your measuring wring them and stack them properly.
    running big parts cost money to do it correctly, if you dont you scrapped huge amounts of money because of using a sub par method of inspection.
    Maybe I should have started a new thread, rather than polluting OX's with other questions.

    Not sure if you noticed what I was trying to inspect in particular...~11ft long plate part, over dimensioned, and +/-.010, or better, range was what I'm shooting for holding. If I needed to inspect the way you are suggesting, I would budget that into the quote, but I dont feel these parts justify it. It's a small job, not likely to repeat, and investing $10k in gage blocks for this would be a little nutty at this point.

    Tom's reply seemed pretty on point for what I was asking, I'd just like to learn some of the finer details, and get a better feel of how others handle this lower precision stuff. Parts that dont justify $10k worth of gage blocks, but a tape measure doesn't quite cut it. And over 5ft in general.

    My concerns with his response involved tolerance stackup with (affordable) micrometer standards, which you addressed, but i think you are referring to more precise parts. As well as support of the trammel tool. It would have to be able to be held in about the exact same way during calibration as the measurement reading, which could be tricky with 11ft of black pipe or whatever.

    After that stuff is settled, maybe there is a thermal expansion argument to be made, but if everything is steel and approx the same temp, I'm not too concerned. Most of the alloys I cut expand at about the same rate as the references I would use, and the way I take these trammel tools to work, you would want to calibrate pretty often...maybe each measurement.

    I'm sold on the Pi tape for round parts.

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    Well, I'm not worried about the polution.

    If someone wants to comments about my original post, there is plenty of room here to doo that.


    As for yours, on some parts that were run on one of our smaller lathes (65mm) but were done hitch after hitch to git to length, I qualified the length by puting them in my big lathe that had enough travel to cover the OAL, and used an indicator and touched it off here, and then run to the other end and touched off the chuck jaws where it was located to.

    Don't know if your mill has enough travel to doo it that way?
    Nor can I qualify how accurate my means was, but the parts didn't come back, so ...




    --------------------------

    Think Snow Eh!
    Ox

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    sorry my bad I wasn't paying attention to what you were running, just as it relates to ox's job on the inspection aspect.

    as far as your situation, you took a gamble and it worked thats great. me myself I wont run a job unless I can be 100% sure of inspecting it.

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    Quote Originally Posted by Delw View Post
    sorry my bad I wasn't paying attention to what you were running, just as it relates to ox's job on the inspection aspect.

    as far as your situation, you took a gamble and it worked thats great. me myself I wont run a job unless I can be 100% sure of inspecting it.
    My job hasnt made it past bid phase yet. Are you really suggesting the only thing better than a tape measure is gage blocks? No middle ground?

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    Quote Originally Posted by Ox View Post
    Well, I'm not worried about the polution.

    If someone wants to comments about my original post, there is plenty of room here to doo that.


    As for yours, on some parts that were run on one of our smaller lathes (65mm) but were done hitch after hitch to git to length, I qualified the length by puting them in my big lathe that had enough travel to cover the OAL, and used an indicator and touched it off here, and then run to the other end and touched off the chuck jaws where it was located to.

    Don't know if your mill has enough travel to doo it that way?
    Nor can I qualify how accurate my means was, but the parts didn't come back, so ...

    --------------------------

    Think Snow Eh!
    Ox
    I wish, My biggest travel with a lead screw is currently 60". Think hanging a 800lb part off the side of bridgeport and doing reasonably accurate work, but 4x bigger. The new machine's table does have 10 ton capacity though.

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    Quote Originally Posted by Hillside Fab View Post
    I wish, My biggest travel with a lead screw is currently 60". Think hanging a 800lb part off the side of bridgeport and doing reasonably accurate work, but 4x bigger. The new machine's table does have 10 ton capacity though.
    Thats not quite true...I have an engine lathe that could traverse 12ft, but I seriously doubt the accuracy of the screw over that distance. And my own counting ability.

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    Quote Originally Posted by Hillside Fab View Post
    My job hasnt made it past bid phase yet. Are you really suggesting the only thing better than a tape measure is gage blocks? No middle ground?
    for ox's job yes. for your job I have no clue

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    In my case, the big lathe was CNC with ground ball screws.

    Not exactly a 60 yr old acme lead screw....


    ----------------

    Think Snow Eh!
    Ox

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    Quote Originally Posted by Ox View Post
    In my case, the big lathe was CNC with ground ball screws.

    Not exactly a 60 yr old acme lead screw....


    ----------------

    Think Snow Eh!
    Ox
    Haha yeah, that's why I didn't even think to mention it at first. Even if the screw was new, it seems like it would be a pretty frustrating exercise.

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    Probably a bit late in the day but a thought. Calipers (digital) are accurate enough to measure a ±0.005" tolerance at 38" if you have a rod that is 38" or close.

    Comparison measurement with a digital caliper gets a much more accurate result than when "just" starting from zero.

    There are also "lightweight" digital calipers on the market if weight is a concern.

    There are others than Mitutoyo (552-193-10) for 0-40" so this is just one example. With an accuracy of ±0.002" without a reference rod it could be interesting.
    With a rod then even more accurate.

    Price? I've no idea

    MEASURING INSTRUMENTS CATALOG No.E2018

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    Quote Originally Posted by Gordon B. Clarke View Post
    Probably a bit late in the day but a thought. Calipers (digital) are accurate enough to measure a ±0.005" tolerance at 38" if you have a rod that is 38" or close.

    Comparison measurement with a digital caliper gets a much more accurate result than when "just" starting from zero.

    There are also "lightweight" digital calipers on the market if weight is a concern.

    There are others than Mitutoyo (552-193-10) for 0-40" so this is just one example. With an accuracy of ±0.002" without a reference rod it could be interesting.
    With a rod then even more accurate.

    Price? I've no idea

    MEASURING INSTRUMENTS CATALOG No.E2018

    I checked the link. Can not zoom in on anything. Are the jaws for that size 20" (a little over half his projected size for a round part)? How would you do that with calipers? Extensions?

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    Hillside Fab,
    There are some magnetic tapes available that are used with a linear encoder and a DRO console. Maybe fab something using that stuff. Or how about a trav-a-dial and a linear rail with an indicator attached and clamped right on your part. Hard to envision exactly what your trying to accomplish here. Overall length can sometimes be measured pretty close by moving as far as you can accurately then putting a reference pin there, move the part and pick up the pin location and do it again. Never did a 12 footer but I've done longer than table travel on a Bridgeport.
    Seen that done on a jig mill too.
    spaeth

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    Quote Originally Posted by spaeth View Post
    Hillside Fab,
    There are some magnetic tapes available that are used with a linear encoder and a DRO console. Maybe fab something using that stuff. Or how about a trav-a-dial and a linear rail with an indicator attached and clamped right on your part. Hard to envision exactly what your trying to accomplish here. Overall length can sometimes be measured pretty close by moving as far as you can accurately then putting a reference pin there, move the part and pick up the pin location and do it again. Never did a 12 footer but I've done longer than table travel on a Bridgeport.
    Seen that done on a jig mill too.
    spaeth
    Work is on a HBM, it's a plate about 2" x 2ft x 11ft.

    I just mentioned the part hanging off the bridgeport scenario to help visualize a smaller scale version of what I'm trying to do.

    I will need the pins/tooling balls to shuffle the part around to reach everything. I was thinking this wouldn't be sufficient for inspection due to potential for error, but nothing is probably that critical anyway.

    Thanks.

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    Quote Originally Posted by Hillside Fab View Post
    Not sure if you noticed what I was trying to inspect in particular...~11ft long plate part, over dimensioned, and +/-.010, or better, range was what I'm shooting for holding. If I needed to inspect the way you are suggesting, I would budget that into the quote, but I dont feel these parts justify it. It's a small job, not likely to repeat, and investing $10k in gage blocks for this would be a little nutty at this point.
    If you need to inspect work that size/tolerance with any regularity, I would be looking at a Faro/Romer arm.


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