Measuring concentricity between 2 bearing axis
Measuring concentricity between 2 bearing axis
(OP)
How do you measure the concentricity of the 2 bearing journals in the same plane.
Thanks
SLTG
Thanks
SLTG
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Measuring concentricity between 2 bearing axis
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RE: Measuring concentricity between 2 bearing axis
RE: Measuring concentricity between 2 bearing axis
Cheap but effective, probably good for in field usage.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Measuring concentricity between 2 bearing axis
Like a motor shaft that is to connect to a pump shaft.
If it is a common shaft, then it can be located in a lathe or vee blocks or rollers or bearing halves, and while rotating it you would see a wobble if they are outa line, except in a lathe where you would just indicate each journal separately.
RE: Measuring concentricity between 2 bearing axis
maybe I don't understand correctly, but how do I know that the axis of the first journal is perfectly lined up with the axis of the second journal. It is a common shaft.
SLTG
RE: Measuring concentricity between 2 bearing axis
If the distance is short and you are using babbitt bearings then bluing on a known straight shaft will also give some indication of the relative alignment.
Good luck
Ralph
RE: Measuring concentricity between 2 bearing axis
You would have to know how to use an indicator and height gauge or surface gauge, and surface plate to check it on Vee blocks. If it is a very large shaft, you will have to use either laser or optical alinement of some sort. Ralf2's idea will work too. It may help if we know the size and use of the shaft.
RE: Measuring concentricity between 2 bearing axis
I'm sure it's possible to automate the process, and I'm sure it's been done. I'll conjecture a labor- intensive process that could be done with tools that I might be able to get.
Set up four sensitive dial indicators, one at each end of each journal. Using a degree wheel, spin the shaft slowly on whatever axis can be arranged; between centers, journals on v-blocks, whatever. Every few degrees, record the reading of each indicator. Complete one revolution.
In a CAD program, draw four perfect circles in 3D space at the locations on the crank axis where the indicator measurements were made. Rotate your coordinate system, and for each data record, draw a radial line away from the perfect circle corresponding to each indicator's reading in the appropriate direction.
Then fit four perfect circles to the ends of the radial lines you've drawn. Or draw polylines enclosing those line ends, close the polylines, and find the centroids. Now you've got two points in space that define the ends of each journal's axis. Draw a line between them, extend it to whatever measuring plane you'd like to use, and find the difference in the intersection points of the two lines with the measuring plane.
Of course, you can do the same thing with numbers in a spreadsheet, but I thought the graphical description might be more illuminative.
-Mike-
RE: Measuring concentricity between 2 bearing axis
RE: Measuring concentricity between 2 bearing axis
The shaft is 3 feet long and 2" OD
SLTG
RE: Measuring concentricity between 2 bearing axis
RE: Measuring concentricity between 2 bearing axis
Typical ball or roller or plain bearings probably don't care about 0.0005 inch or so.
2 narrow not-very-precise v-blocks, a test indicator, and a 2 inch micrometer in the hands of a decent imaginative inspector should indentify any problem.
Measuring between centers can be deceiving. An excellent shaft with a buggered center spins the indicator needle pretty good.