SPLINE CLARIFICATION PLEASE 2

[MRSSPOCK]

Hi.

Could someone please clarify the apparent discrepancy shown here in the attached image.

(I say apparent because I simply don't understand, so they may well be accurate indeed).

The illustration is from the machinerys handbook, and seems to suggest that a fillet root spline doesn't necessarily have a full rad, i.e. rfi = 0.4m but if Full radius is smaller, use full radius.

The comment at the bottom of the image is from

http://www.gearsolutions.com/article/detail/5604/inside-splines

which states it is a full form rad.

Thanks

 

[Occupant]

What standard are you using? DIN 5480 shows a root fillet of 0.16*M

 

[MRSSPOCK]

@ occupant

I'm not using any standard.

I don't even have a spline.

I'm just reading up on the subject and trying to understand, when I came across this apparent contradiction, and hoped someone could explain it.

 

[mfgenggear]

Mrsspock

here are 3 attributes of many that need to satisfy the specification.

the root diameter size
the fillet radius specified.
and the fillet radius must clear the form diameter.
the size of the fillet radius can not interfere with the form diameter(TIF) prevent interference with mating part.
so it may be limited how large it can be. and it will vary from design to design.

that said, if a minimum fillet radius is specified it can well become a full radius
if it meets the criteria as noted above. this is the simplified explanation.

now if the designer needs a full fillet it must be specified and it (the design)
must clear the TIF so there is no interference with the mating part.

Mfgenggear

 

[CoryPad]

The drawing comes from ASME B92.2M, which I just reviewed to make sure it agrees with Machinery's Handbook (it does). You can see from the image that the root fillets are dimensioned from two locations, so it is implicitly saying that a full radius in the root is not expected all the time.

 

[MRSSPOCK]

@CoryPad

@mfgenggear

So, it appears that you agree this following statement isn't accurate ?

"The fillet root side fit spline exhibits a full radius in the trochoid area between the teeth on both members."

Should it really state,

The fillet root side fit spline, sometimes exhibits a full radius in the trochoid area between the teeth on both members.

Thankyou

 

[mfgenggear]

Mrsspock

Correct, as stated if it does not specify full radius required
as long as it meets the minimum fillet radii it is in conformance.

Mfgenggear

 

[MRSSPOCK]

Dead on.

Thanks for your help.

 

[tbuelna]

I checked my copy of ANSI B92.1 and section 7 covers fillets/chamfers for various types of splines. One consideration discussed is the method (hobbing, shaping, etc) used to produce the spline. For example, if an external spline is produced by rolling it will usually end up with a full radius fillet.

The type of spline shown in the OP example is a "fillet root" spline, but does not necessarily require a full fillet radius. For fillet root, side fit splines having a 30deg PA the ANSI B92.1 spec simply requires a minimum root radius for both internal and external teeth as defined in table 108.

Per ANSI B92.1 30deg PA major diameter fit splines, the internal teeth must have a root fillet that clears the external tooth tip chamfer dimension listed tables 17 thru 24. The size and shape of the external spline root fillet is optional, as long as it conforms with other dimensions listed like form diameter/clearance.

Generally, the root fillet stresses of the external teeth will be higher than for the mating internal teeth. So it would be beneficial to use as large a root fillet radius as practical at least for the external teeth.

 

[MRSSPOCK]

@tbuelna

Thanks for taking the time to investigate my query, and for your in depth clarification.

It makes much more sense now.

Thanks again.