Is there a reason to have slightly different lead crowning on left & right flanks of external sp

rollingcloud

it depends on the geometry of the spline, , if it has clearance for hob, shaper cutter , and grinding wheels. the old days it was control by mechanical means with a cam.
these days it is controlled by cnc software. one has to under stand what a crown spline is required for that would be for mis-alignment. splines are notorious for fretting and wear, due to lack of lubrication. so it has to be robust and s/n curves really have to scrutinize. thus to prevent contact errors a crown spline profiles and outside diameter must be crowned. .00015 error will be no effect. and that is why there has to be a tolerance for both sides of the crown. because of the mechanics, it is not always an exact science.

Thank you for the response. By geometry, you mean DP/module? So for a DP of 1.6875, 0.00015 is too small of a difference to be an intentional design. So typically, lead crowning and major diameter crowning goes hand in hand?

rolling cloud

do have an actual spline data that you can share and the geometry of the spline

Mine definitely has both lead & major dia crowning, topland radius is about 0.8. I was just wondering if it's common.

number of teeth 27
spline pitch 16/32
pressure angle 30
base diameter 1.461418
Major Diameter (max) 1.750
Form Diameter 1.621
Minor Diameter 1.564
MAX EFF CIR Tooth thickness 0.0982
MIN Actual CIR Tooth thickness 0.0953

rollingcloud

so for the example above the standard spline the max tolerance for a standard straight ANSI B92.1 -1996 is for 1/2 inch long .0003 " max tolerance, for one inch long .0004 inch tolerance.
so s crown spline will have a gauge point usually like .00015 - .00035 crown as an example. as longs as both sides and flanks are in tolerance it is good. yes it is common to have a crown on the od to prevent contact error, and especially for a major diameter fit spline.

Does the inspection result from analytical gear testers accounted for plating thickness?
I got lead variation range from 0.00047 to 0.00075 on this fillet root side fit external spline. Should I subtract the plating thickness (0.0003 - 0.0005) from the inspection results? The face width is only about 0.25'', which means the max lead variation is 0.0002 right?

rolling cloud

yes .30 and under is .0002 max.
The plating thickness would have to be controlled by the measurement over wires. or a go gauge pre plate.
regardless of plate the inspection criteria would have to be after plate. parts must assemble. a set of gauges go and no go would tell you that.

Thank you for the quick response!
So the analytical gear machine generates standard/nominal involute profile and the inspection results are compared to the that nominal profile, meaning I do need to deduct plating thickness from the inspection result such as profile variation & lead variation, correct?