Involute Spline 3

[slickstyles5]

Hi,

I am currently trying to design an involute spline (female) that will fit on an existing male spline. I don't have much info of the spline and it makes it complicated and I don't know which standard is used. Here's the information I have:

36 Teeth
30 Degrees Pressure Angle
.498"/.499" OD
.463:/.467" ROOT DIA.
.485" PITCH DIA.

Does this spline represent a standard?

Thanks

Gabriel

 

[dinjin]

It probably is a 1.5 Module System.
It might also be an 18 Diametral Pitch System.
Where was it made?

 

[dinjin]

Another Standard is the 18/36 30 degree involute spline standard.
Somehow, you are going to need dim over balls or pins, or know the tooth thickness.

 

[slickstyles5]

I have an arc tooth thickness that seems to be approximately .212" if I am reading it correctly. Does this help? It is from an aircraft engine manufactured in the US.

Would anyone have a table of the 1.5 Module system or 18 DP system so I could check it out?

Thanks!

 

[dinjin]

Sorry to lead you astray.
if d equals N/p, then p must be
approx 72 to 74.
It must be a special design.
Very certain it is not a module design.
Your arc tooth thickness of .212 looks
off by a factor of 10.
I would think it would be .0212 or
greater.
What function does the spline have?

 

[gearguru]

dinjin/galeblanc:
the module 1.5 spline with 36 teeth has the pitch diameter 1.5*36=54mm (2.126in).

The inch based spline with pitch diameter .485" has the diametral pitch 36/.485=74.2268

Some data are probably just approximate. Is it from a drawing?

 

[slickstyles5]

Yes it is from a drawing from an engine manufacturer. I am not an expert, neither is our company, on these types of splines. We just need to figure out the details of the spline in order to adapt to it with a custom part. This spline is used as a throttle for the engine and we must attach to it and apply a max torque of 17 in-lb to turn the spline shaft.

After rechecking, the arc tooth thickness is 0.0212" as mentionned by dinjin. Does this confirm anything?

Please let me know what I could possible attempt doing at this point? Am I missing some data to be able to fabricate something? Does anyone have a basic spline calculation design guide to calculate the missing parameters?

 

[gearguru]

The arc tooth thickness is measured / calculated on the pitch diameter, correct?

 

[dinjin]

You almost need three measurements to determine the
involute unless you know the specific diametral pitch.
I had chose 72 as the nominal as I thought it might
be the most common. But as gearguru pointed out it
might be 73 or 74. It is such a small gear that
possibly 3 dimensions over 3 different size pins
and balls might be required. Maybe you can get some
piano wire or something to check out the dimension
over pins. You might need .024,.0245,and .025 diameter
pins or .60mm, .62mm, and .635mm dia. or combination
of any of these inch and millimeter pins.
Chordal reading at different depths might also be
used. I do not think you could buy a small rack
of this size, but if possible you could use that
to check out the rolling effect to verify the little
spline. How many teeth are in the internal motor
spline or is it an external spline? I just assumed
72 diametral pitch because of the whole depth.

 

[WinstonH]

galeblank,

When the external is hobbed, it is involute form & accepted as it is so slight a deviation from straight.

Dimensions listed are for the old SAE J500 straight serrations,
1/2-36.[About 1962].
I may have posted long ago on my Photo-bucket account I'll check & get back.

Cheers,

 

[WinstonH]

Here you go,

and,

Lists full data wire size etc.

Cheers,

 

[slickstyles5]

Wow WinstonH!! That's quite incredible what you provided there. This is perfect, thank you very much!!

 

[gearguru]

galeblanc,
your spline is an involute spline with 30 degrees pressure angle.
WinstonH's documents apply to straight serrations (45 degrees). Not the same animal at all.
You should hire a professional to design your spline.

 

[slickstyles5]

gearguru,

I'll have to double check everything but the numbers seems dead on and even the tolderances min/max are the same numbers (sahft OD min/max, pitch, root dia.). I would tempted to say it seems right, but I'll double check in the morning at work.

Thanks for the heads up!

Gabriel