PITCH DIAMETER DATUM

[[Na...]]

I have internal spline plug gauge. I am trying to recalibrate the gauge. my question is how can i take alignment pitch diameter as a datum in zeiss software . we don't have rotary table we check spline horizontally. i take major diameter as a datum but it is not working as Fp is way out than it supposed to be and we know Fp is not bad at all. Thanks

[[Ch...]]

Nasir,

Hi. Welcome. With pitch diameters (which are theoretical it can can be challenging to establish).

With a spline gauge you are correct to use the pitch diameter as datum. It sounds like you have a spline plug gage for inspecting internal splines. Either way both plugs and ring gages are typically manufactured with a ground 'concentric' ring band on the gage. Ring Gauges however have end faces which may be ground, and common inspection is to locate on an end face, but if gauge drawing does not specify this as a datum - or the conc. band as a datum, by default the datum is to itself which is the P.D. as you mentioned. Spline plug gages sometimes do not have a conc. band and are manufactured to "centers".


There are a few ways to establish the P.D.. For a plug gage (external spline to inspect/gauge internal splines), best way is to visually and programmatically line up one gap of the spline (to +Z if inspecting horizontally, etc.) and self-center the specified gage ball (for M.O.P.) in each gap all the way around at the top and bottom and use the probe midpoints to establish the pitch cylinder. If you have a similar size diameter probe ball (< ~ .010" difference) you can probably use it with similar results, however more than this and you will be contacting the flanks in a different location and could lead to inaccurate results.

Do you have gear pro as well ?

Are your tolerances similar to this : Fp .0002", Fr < .0004" Fß .0001" Fα .0002" ? You will need to make sure everything with your set up and programming is accurate and precise to meet these tolerances.

Spline No-Go should be verified as well, however this is challenging, especially if there are only 4 teeth, and only the gap between each 2 are ground and used. (even more challenging if it is based on odd # of teeth) - but it can be done, maybe just one flank at a time.

Good luck.