Measuring a lathe spindle on a surface plate
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  1. #1
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    Default Measuring a lathe spindle on a surface plate

    Hi everyone,

    As some may already know from my other thread, I'm in the middle of a process of screwing up my Hardinge HLV-H clone ( Can anyone tell me why did I take apart this Hardinge spindle? ).

    I just feel that it's more appropriate to discuss measurement-related part of that here, in "Metrology".

    I want to accurately inspect/measure a spindle shaft, that I took out. I'm interested in runout, straightness, roundness and concentricity with .0001" accuracy.

    Here is a measurement setup that I came up with: bearing surfaces of the spindle lie on AA grade gage blocks 0.500" each. 1-2-3 blocks are stopping the spindle from rolling. I wiggle an indicator back and forth to find the maximum and I assume it's a relative diameter of that particular spot. Then I will move the indicator along the spindle. And then I will rotate the spindle 45 degrees at a time and repeat.

    Ideally, I'd like to get some sort of a map of diameter deviations along the spindle. I can double check the measurements looking at values that are 180 degrees apart. If I get it right - those values should match.

    All the instruments were recently calibrated.

    A separate question: how do I measure concentricity/roundness of outside/inside tapers on a spindle nose? I somehow need to do measurements at the exact same position on the shaft.

    Thanks!

    img_5337.jpgimg_1885.jpg

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    Why aren't you using V blocks? That would be the correct way to measure this imho. Use the shoulder of the spindle against the edge of the V block to measure the taper at a set distance. May have to clamp the V block to the surface plate.

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    Quote Originally Posted by RJT View Post
    Why aren't you using V blocks? That would be the correct way to measure this imho. Use the shoulder of the spindle against the edge of the V block to measure the taper at a set distance. May have to clamp the V block to the surface plate.
    My V-blocks are not calibrated and I don't trust them. Does using gage blocks versus V-blocks affect measurements or it's only a matter of convenience?

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    It would be a whole lot easier and more accurate with V blocks. As long as they don't rock or move on the surface plate, it should be fine. The idea is you can spin the spindle in the V block and leave the indicator stationary to get runout, and coincentricity. Straighness will depend on your V blocks, you can use your 1-2-3 blocks for that.

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    duuuuude....

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    Quote Originally Posted by iwananew10K View Post
    duuuuude....
    Thank you for the very helpful and well elaborated comment!

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    Don Bailey did a tour of a spindle shop. Well worth a watch all way the through but they show some inspection at 9:10
    What it takes to remanufacture a spindle

    I think RJT has it, as long as your Vee blocks arnt rocking on the plate you should be good. Notice the less than precision bit of something he has packing out the spindle near the rear bearing.

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    by looking at the pictures in the 1st post I can't even tell what you're trying to measure

    put 2 V blocks of equal height under the places where the bearings mount, indicator on the spindle nose, carefully spin the spindle on the V blocks to get the idea of how true the spindle nose is to the bearing seats, if it within reason, you can stop there, after marking high (or low) point for later reference, edit: you can and should also check the roundness of the bearing seats themselves, also mark irregularities

    you see that you don't need "calibrated" V blocks for this, actually any stationary setup will do, you simply want the spindle to not move around axially or radially when you turn it, that is it

    if the spindle nose shows gross errors, you can further investigate by indicating at different places to get the idea where the error comes from (if you suspect it could be bent), if the bearing sets and middle measures fine, you might get away with just a spindle nose regrind

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    Quote Originally Posted by Frigzy View Post
    My V-blocks are not calibrated and I don't trust them. Does using gage blocks versus V-blocks affect measurements or it's only a matter of convenience?
    You do not need calibrated v blocks, just a matched set. Check them with a class x or xx gage pin. By indicating front to back on both you can tell how closly matched they are. I use the Starret 568's which are almost perfect; maybe .00005 difference. When using them on different size diameters subtract smaller from larger (diameter) and multiply the difference by sine 45* (.7071) and this is the amount needed place under the small diameter v block
    to level your shaft centerline.

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