I need a measurement method



Hi All!

Anyone who can give me an idea will be much appreciated!

Here is my problem: we run a motor shaft various lengths and diameters, but the problem I have is there is an output keyway on the end and it has to be centered in the diameter of the shaft and cannot be off by more than .001. but the shafts are to long to fit in our comparators. I have not been able to find any other way to check to make sure they are on center other than visually and you can see where that would be a disaster at times. I can supply a print if anyone cares to take a stab at an answer!!

-the keyways are cuts in the end of the shaft and are different widths depending on the diameter of the shaft they also vary in length and depth. Also I need this to inexpensive!!!!

Help if you can
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Bill Ryan - 2007

Hi Connie.

Just a quick thought off the top of my head. Is a "functional gage" a possibility (something that might capture the shaft diameter, RFS, with a male member that would seat into the keyway)?



Hi Bill

We thought of doing that but....
We would have to make one for each shaft and there are so many different sizes that it would cost to much if you figure haveing to purchase all the different ring gages to size and then trying getting the keys which are all different sizes as well. Plus then there is a storage issue too.

I thought of using autocad to create a visual of each different keyway end with the keyway indicated using crosshairs to center it on the shaft and try to check it this way visually (These would have to be printed on clear tranparency film). what do you think? I haven't had time yet to try it.

Thanks for the input though!!!!
Last edited by a moderator:
Hullo Connie,

Some guesswork on my part:

Just maybe a functional gauge would be a good idea after all…
I suppose you line the shafts up using the dowel holes when you cut the keyways? If so, a gauge could line up on the center line (the dowel hole, which I presume is the datum for the keyway position anyway) instead of the diameter.

Then it’s a matter of positioning the simulated mating key accurately enough.

Could that work?







Proud Liberal

Quite Involved in Discussions
keyway location

A functional gage wouldn't work because the width tolerance of the keyway would cancel out the resolution on the gage since it would have to be designed MMC. This needs to be evaluated RFS.

If you can fit the shaft on a pair of "V" blocks, you can check this easily on a surface plate.

1. Insert gage blocks into keyway (snug fit to size of keyway).
2. Rotate shaft on "V" blocks until top surface of gage block is parallel to surface plate.
3. Measure height of gage blocks.
4. Measure height of shaft.
5. Determine C/L of blocks (block height - ½ block thickness)
6. Determine C/L of shaft (shaft height - ½ shaft Ø)
7. Subtract shaft C/L - block C/L
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