What type of fit is this internal spline? 1

[rollingcloud]

I know I have another thread going on but this is slightly different topic, so I wanted to create a new thread.
number of teeth 27
spline pitch 32/64
pressure angle 30
base diameter 0.7307089

Inspection results:
no modification
min minor dia: 0.81307 inch
max minor dia: 0.81772

min major dia: 0.90230
max major dia: 0.90651

min size between balls: 0.74993

The root definitely has two fillets when zoomed in at 50X, but I cannot tell if its major diam fit or flat root side fit since both bottoms can be flat, I don't have the mating spline shaft data for this internal spline.
Since inspected major dia exceeds ANSI limit for max major diameter for the flat root side fit, can I say its major diam fit? ANSI B92.1 does not have the table for 32/64 major dia fit data.

EDIT: The max minor diameter exceeds all of the popular standards such as ANSI, SAE, J500 and AIA/NAS 580 ...I guess this is not a standard spline after all...

 

[spigor]

What was the diameter of wires used for the MBW?
At a first glance, this looks like a B92.1-1996 DP32/64 30PA fillet root side fit internal spline.

 

[rollingcloud]

Ball diameter is 0.060 inch, the measured max minor diameter exceeded the ANSI standard by 0.0017 though, everything else is within the Ansi tolerance

 

[spigor]

Well, the minor diameter looks to be 0.0017 off the tolerance in B92.1-1996.
Your ball measurement translates to 0.0517 circular space width and that is within the Class 5 tolerance (max circular space width specified in B92.1-1996 for Class 5 is 0.0518).

 

[mfgenggear]

rolling cloud

know the difference between a fillet root side fit, flat root side fit, and a major diameter sit fit and what they are used for.
never assume , that will cause you issues.

 

[mfgenggear]

yes this meets the criteria of a fillet root side fit

 

[rollingcloud]

spigor

I was not thinking straight, I just realized since the ANSI is within the measured tolerances, its safe to use the standard in this case since standard tolerance is just tighter. The average minor dia is about 0.815 which is also well within the ANSI tolerance.

 

[rollingcloud]

mfgenggear

From my understanding, major diam fit can be used in fixed spline, such as spline on an output shaft spline. Fillet root side fit splines are flexible splines that permits heavier loads, such as coupling applications, flat root is similar to filet root but used when fillet root is not an option. Based on what I have seen using the optical comparator, majority of the roots appear to be full fillet while some appear to be flat root, therefore, I can probably say its fillet root side fit and rule out the possibility of major diam fit, even though this is going to be a fixed spline.

 

[mfgenggear]

I tried to find a free copy of Dudley's when splines needs stress control, also look at zakgear external spline based on Dudley's formulas

https://www.zakgear.com/External_Spline_IN.html

the spline configuration is based on the stress and loads required, for example when a fillet root does not have enough land, or rim a fillet root will not suffice, a flat root is required. search splines on eng tips with
past post, there are a lot of great engineers that posted about spline designs. tbuela was one of them.

 

[rollingcloud]

mfgenggear

Thank you very much for the zakgear calculator, looks very handy for external splines.
I found Dudley's guide at:

https://documents.pub/document/when-splines-need-stress-control-dudley.html

From initial reading, there is no mention of different types of root/fit though, but somehow, I feel it must be hidden somewhere in another factor, I will dig deeper over the holidays.
"Generally, the "fixed" spline (which mounts a gear, pulley wheel, turbine wheel, etc., in contrast with the
"flexible" spline used as a coupling between shafts) has no relative motion between internal and external
teeth to cause wear." -- Dudley

What is confusing me is that since all type of fits has certain degree of backlash, how can you have no relative motion with backlash? I might need to create a little animation for myself to visualize the difference between motions of fixed spline & flexible spline
I am having a minor fever right now, so maybe my brain is too fogy for this...