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

[rollingcloud]

Analytical inspection showed consistent average difference of 0.00015 between right & left flanks, with 4 samples, I am guessing its most likely inspection error + manufacturing error, but since splines are very intricate, I can't be sure if it's intentional, if it is, what would be a reason to do that? The spline itself is ANSI class 5/6, it's a shaft with external & internal spline that's used in high torque environment, can someone shed some light here please

 

[mfgenggear]

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.

 

[rollingcloud]

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?

 

[mfgenggear]

rolling cloud

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

 

[rollingcloud]

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

 

[mfgenggear]

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.

 

[rollingcloud]

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?

 

[mfgenggear]

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.

 

[rollingcloud]

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?