PITCH DIA AS A DATUM

[[Na...]]

I have a tube which has spline on one end. Customer wants to know concentricity for one diameter against pitch diameter of spline. Can you guys please help me on how to take Pitch diameter as a datum. what strategy should i adopt or any pattern is involved. Any kind of help would be appreciated. Thanks

[[Ch...]]

Have you tried as I suggested in original post in Gear Pro section ?

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[[Mi...]]

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**I am not a gear guy, just slowly learning as we have fairly simple splines**

Self Centering points with the correct sized ruby as Chris suggested in his reply to your other post is what we do. Did that not work?

[[Na...]]

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[[Na...]]

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[[Ch...]]

Nasir,

So the minor difference between the self centering points, and points on the flank are :

self center points need a datum center ( bore of spline plug gage) to get to the measuring point location. The self-centering points ,while they need the bore to define the nominal, the do not require to be clocked to anything accurately. They are independent, and can construct an independent circle.

If you do not have proper ball size to self center in the gap, and measure points on the flanks, it could lead to slightly decreased accuracy for 2 reasons :

1.) to get to the points on each flank ( for the pitch diameter) you first need an X/Y 0,0 (datum bore, etc). Depending how this is measured, it could add error to the location where it actually measures the pitch.

2.) you also need to align or 'clock' one gear tooth to pattern the points on the pitch diameter. doing this with single points one the flank could lead to slight decreased accuracy - even if you stop and line up a tooth by eye first. The 2 points on each flank may not be accurate enough, depending on the size of the tooth and pitch diameter, etc. - It may start to drift as it is patterned.

This being said I have used both methods, including the points on flanks to measure position and runout of .001-.002" in Calypso with success. Less tolerance than that and you would need to make sure your set up and measurements are tight, and I think it could be possible.


One other method, is doing an 'index/pitch' test in Gear Pro, this way it feeds into the tooth and lines it up for you. Then you can export stylus tip center points in Gear Pro to a file.
In calypso you make a circle and recall points from this file ... you may need to remove stylus radius compensation etc. and the diameter size may not make sense, but the center X/Y should be accurate.

Good luck !

[[Na...]]

Thanks Chris. It really help me out. I appreciate your help. once again Thanks