Involute Spline 1

[coldformer]

I am trying to design a go gage for an involute spline. I have drawing the spline several ways but the when I draw in the pins and check the diameter it does not match up with the print. Can someone that has a program for creating these splines send me a dxf or something so I can find my mistake?? It is 16 teeth, pressure angle of 37.5 Degrees, tooth thickness of 2.090 +.058/-0.0 @ DP of 19.0mm. Minor Dia. is 18.2 +0.1/-0, major dia. 20.25 +0.1/-0. Once drawn you should end up with a pin dia. of 15.04 +0.05/-0 using 2.5mm pins.

Any help you may have would be great. I have attached my drawings if anyone is interested.

Thanks

 

[mfgenggear]

for external spline in accordance to ANSI B921

your go ring gage is your max effective circular space width.

your no go is your min. actual circular space width.

The max actual circular tooth thickness is reference if
verified with an ring go gage.

In the 1970 version of the above book it is explained in pages 83 & on.

 

[mfgenggear]

for an Internal spline ANSI B92.1 fillet/flat root side fit.

max circular space actual is used to calculate your no go plug gage.
minimum effective space width is used to calculate your go plug gage.

your minimum actual circular space width becomes a reference if a go plug gage is used.

you can not use wires to verify your min. effective size.
because it includes all of your errors, tooth index, lead,
involute ect. ect ect.

Hope that helps.

 

[coldformer]

Thanks for the input, I think I understand your response. I am not looking for wires to check the spline profile, I am looking to construct a go gage. In order to cut it on my wire EDM, I need to consturct a dxf file. I do not know how to do this with Autocad or Solidworks which are the two programs I know how to use. When I was looking around on the internet I read about some special programs that you can plug the numbers into and they give you the dxf. I was hoping someone may have access to one of these or could tell me were to get one. I don't do this very often so I don't want to spend a lot of money on it.

Thanks again for your help.

 

[gearcutter]

From your attachment it appears that you are not using an involute curve for the sides of the teeth. The straight lines you are using are not appropriate for what you are trying to do. This explains the problems you are having.

I can create the DXF for your wire cutter but it will cost you.

You can contact me via the link below.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[coldformer]

I understand the lines are straight, this is what I do not know how to do correctly in Autocad. I send you my contact information so you could provide me with a quote.

Thanks for the response.

 

[chicopee]

Which ACAD version do you have? I can not open it w/ 2004 can you send it in that version?

 

[coldformer]

Attached is a 2004 version.

Thanks for looking.

 

[chicopee]

This is definitely not an involute spline. To generate an involute tooth profile, wound a string around a circle and keep the free end taut and on the surface of the circle. Imagine a pencil attached to that free end, unwound the string and let the pencil lead describe a pencil mark as you keep unwounding the taut free end. The path described by the pencil lead is an involute one.

To learn more about tooth profiling, gears and splines I suggest that you either go on line or get a current Machinist Handbook. The machinist Handbook has a table to calculate the many parameters of an involute tooth profile so that you can draw it in ACAD.
Good Luck!!

 

[dinjin]

Your drawing is not an involute spline and you cannot
approximate it by using 75 degrees as the included angle.
The angle would actually be nearer 54 degrees from the
layout that I made. Is the 2.090 tooth thickness actually
the tooth space? Your drawing indicates an internal
spline.

 

[mfgenggear]

Coldformer

I also have a dedicated program that draws gears or splines.
but I only use it on my projects.

if you do a search here on this board there was some one who wrote a lisp programe that would draw the Involute curve
of the gear or spline.
it was very simple to run in auto cad.

making gages is a tricky business. Normally it is verified with gear inspection equipment. since it is a gage, it is held to very tight tolerances. Spline gages are ground
.0001 max parrallel
.0001 max involute
.0003 max index error

however if it were a ref gage for manufacturing then it would be acceptable.

 

[coldformer]

dinjin,

Thanks for the responce. Yes since the drawing in of an internal spline (that I want to inspect with and external gage) the tooth thickness shown would become the tooth spacing on the gage I want to construct. I understand these drawings I attached are incorrect I only wanted to show what I was trying to accomplish. I need a gage to check that the tooth thickness and pin diameter are correct. I dont even need to check the major and minor diameters. I thought I could do this with a straight tooth gage but after I started making drawings I realized I could not.

 

[coldformer]

mfgenggear,

My reason for creating this "gage" is only a reference gage for manufacturing purposes. I am not looking to create a certified gage for inspection.

I tried to search for the forum you are speaking of becasue someone esle told me the same thing but all of them I find the links don't seem to work anymore.

 

[dinjin]

I drew the involute, dimension under 2.5 pins and get
a tooth space of the internal spline equal to your dimension
under 2.5 diameter pins.

Tooth thickness of 2.090 +.058/-0.0 @ Pitch Diameter of 19.0mm would be the tooth thickness of the external spline.

 

[dinjin]

These are the approximate coordinates along the involute
curve on the left hand side. You will have to use the pline command to draw a curve thru these points and trim
the curve at you minor diameter. I assume this is enough
accuracy for you. You will have to rotate the curve about 0,0 position until it is tangent to the pin diameter.

at point X=-1.690885 Y= 7.350665 Z= 0.000000
at point X=-1.693748 Y= 7.367844 Z= 0.000000
at point X=-1.697442 Y= 7.396875 Z= 0.000000
at point X=-1.701055 Y= 7.438197 Z= 0.000000
at point X=-1.703616 Y= 7.492355 Z= 0.000000
at point X=-1.704068 Y= 7.560010 Z= 0.000000
at point X=-1.701227 Y= 7.641947 Z= 0.000000
at point X=-1.693744 Y= 7.739084 Z= 0.000000
at point X=-1.680055 Y= 7.852489 Z= 0.000000
at point X=-1.658317 Y= 7.983384 Z= 0.000000
at point X=-1.626330 Y= 8.133159 Z= 0.000000
at point X=-1.581440 Y= 8.303379 Z= 0.000000
at point X=-1.520415 Y= 8.495787 Z= 0.000000
at point X=-1.439287 Y= 8.712295 Z= 0.000000
at point X=-1.333145 Y= 8.954966 Z= 0.000000
at point X=-1.195867 Y= 9.225962 Z= 0.000000
at point X=-1.019774 Y= 9.527449 Z= 0.000000
at point X=-0.795173 Y= 9.861437 Z= 0.000000
at point X=-0.509750 Y=10.229495 Z= 0.000000

 

[coldformer]

dinjin,

Thanks, I will punch it in and see what I get.

 

[dinjin]

16 teeth
Pressure angle of 37.5 Degrees
Tooth space thickness of 2.090 +0.058/-0.000 @ DP of 19.00mm
Minor Dia. 18.20 +0.10/-0.00
Major Dia. 20.25 +0.10/-0.00
Dimension under 2.50mm Dia. Pins of 15.04 +0.05/-0.00

Involute curve at max dimension under pins, tooth space 2.148mm

at point X=-1.602870 Y= 8.729057 Z= 0.000000
at point X=-1.541855 Y= 8.881664 Z= 0.000000
at point X=-1.407398 Y= 9.167433 Z= 0.000000
at point X=-1.231111 Y= 9.488064 Z= 0.000000
at point X=-1.001721 Y= 9.846206 Z= 0.000000
at point X=-0.704680 Y=10.244040 Z= 0.000000
at point X=-0.542074 Y=10.429985 Z= 0.000000

These are coordinates from minor diameter to major diameter.

 

[coldformer]

dinjin,

Thank you for the points, that was exactly what I was looking for.