Some confusing questions on splines 2

[rollingcloud]

I have two spline parts that's used in high load environment. I have MOW & MBW inspection data for both external & internal splines, is there a formula to deduct plating thickness from the MOW & MBW? So I can confirm the class of the spline.

Internal spline Sleeve - Fillet root side fit - ANSI - CLASS 5
number of teeth 27
Face width: 1.4
spline pitch 16/32
pressure angle 30
base diameter 1.461418
Major Diameter(max) 1.816
Form Diameter 1.754
Minor Diameter 1.625
MIN EFF CIR SPACE WIDTH 0.0982
MAX Actual CIR SPACE WIDTH 0.1011
The internal spline was nitrided to ~57 HRC.

EXTERNAL fillet root side fit spline: class 5
Face width 0.25
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
External spline shows no case hardening evidence and has core hardness of ~44 HRC

Would it better for their hardness to have smaller difference? I wonder why the external spline was not case hardened.

The mating external spline has average lead crowning of 0.0031, lead crowning inspection of the internal spline (see the standard spline data above) shows 0.00005 - 0.00036. Plating thickness: 0.0003~0.0005, can the lead crowning just be the variation of the plating thickness? How do I know if it was an intentional design? From this article,

https://gearsolutions.com/features/a-grinding-solution/

they did a lead crowning of 0.0002 on helical gear.

 

[mfgenggear]

wrong the splines can be designed to standard spline specifications and can be verified with gages, I just said that

 

[rollingcloud]

mfgenggear & spigor

For the crowned spline, the way I understand it is that you can still apply ANSI tolerances at the apex of the crown, the min act CTT & max eff CTT at the apex would still need to meet class 5 dimensions. The min. act CTT & max act CTT would be the same at the apex. Spline gauges can still be made to standard to check max & min eff CTT and min. act CTT (apex).

One thing is still confusing to me is how does the lead crowning affect profile & lead variation measurement? I am guessing there should be no effect on profile variation since the probe should be only measuring at the center/apex. But it would make lead variation incomparable since you would be basically comparing a curve to the straight line?

I am not sure why the vendor stated that ANSI is irreverent in this case, maybe because there would be no machining tolerances if you are only measuring the apex and also lead variation is unmeasurable, these two factors are both part of ANSI B92.1.

 

[mfgenggear]

yes the profile is verified at the center, the specification will still apply less the lead, the gage would verify the center of the crown, the speciation still applies less the lead, remember the engineer can over ride the specification as I said in the beginning. however the total index, profile, al else per the spec. applies. this would be considered a modified spline. but to the specification. max effective on external splines still applies, and min effective still applies in internal splines. the gauges are designed so the the mating splines are assured to assemble. even with plate. and prevents to much plate coating from the supplier.

 

[rollingcloud]

mfgenggear

what do you mean by "apply less the lead"? You mean the lead requirement of the ANSI B92.1 CLASS 5 still applies on the crowned spline?

 

[mfgenggear]

you need to apply a tolerance to the crown height, it will not be a straight lead, the tolerance in the spec is for a straight lead

 

[rollingcloud]

I am starting to feel that the spline sample has no lead crowning, when I look it under 20X optical comparator, it appears to be an almost perfect straight line from the top, if it has lead crowning, it should be curved, with 0.003 crowning I should definitely be able to see it with 20X vision. For some reason the inspection vendor reported lead crowning, I am guessing the operator might have it confused with the top land crowning, which is visible with naked eyes, the radius of the topland crowning is about 0.77 inch. The face width is 0.25.

 

[mfgenggear]

the lead has to be inspected and verified with a lead, or cnc gear checker, it can not be viewed visually.

 

[rollingcloud]

I thought if it has lead crowning, it would look like this example (random sample found online):

The CNC gear checker reported averages of 0.003 for Cβ, so I guess even with 0.003 lead crowning, I would still not be able to see the curvature under optical comparator? I am really lost

 

[mfgenggear]

not all splines require a .003 crown , like said before it depends on the amount of mis alignment. it can vary, as small as .0003 to .005 it depends on the requirements.
on the spline displayed you can see it but you can not tell what the crown height is. and it appears that crown has severe thinning at the ends is I bet it's more than .005 crown.
which make it possible to have severe reduced loads.

 

[rollingcloud]

For now, I am just trying to match the inspected sample.
Are you saying that even with 0.003 lead crowning, it's still normal to not be able to see the curvature under optical comparator?

 

[mfgenggear]

take it to a gear shop and have it inspected

 

[rollingcloud]

It was inspected by a gear shop

 

[rollingcloud]

Okay, it makes perfect sense using CAD, the topland crowning makes it look concaved which is opposite to the effect of lead crowning when looking straight on the topland, thats why the topland looks straight even under 50X. I knew I was missing something simple