Upshur gears

[Harglo]

Upshur Plans call for 20 degree PD gear cutters.
I have the correct cutters, but are for 14.5 degree ptich.
Can I get by with the same gear center distance for an ok mesh, or if not, how much change would I have to due in what direction?

 

[GreenTwin]

There are programs online where you can plug in the information, and it will give you specific gear data for a given size/cutter/etc.
I have substituted different gear sets that have different tooth counts, but the same tooth ratio (2:1), and the same center-to-center distance.
The gear experts will have to chime in here, but I suspect you could substitute gears and make it work.
.

 

[Jasonb]

There will be no difference if you use th e14.5DP, OD, tooth count and gear centers remain the same.

 

[Harglo]

There are programs online where you can plug in the information, and it will give you specific gear data for a given size/cutter/etc.
I have substituted different gear sets that have different tooth counts, but the same tooth ratio (2:1), and the same center-to-center distance.
The gear experts will have to chime in here, but I suspect you could substitute gears and make it work.
.

Many thanks yes em sure will get other info.
Harvey

 

[timo_gross]

I would say, you are good to go as long as you keep center distance and ratio. (pressure angle does not change center distance)
I used 0.5 module gears and did a profile shift. (gears run smooth)
e.g. 40/20 48DP has 0.625" Center distance and 42/21 Module 0.5 has 0.6201" center distance. Leaves only a small difference.

https://evolventdesign.com/pages/center-distance-calc

Greetings Timo

 

[Harglo]

I would say, you are good to go as long as you keep center distance and ratio. (pressure angle does not change center distance)
I used 0.5 module gears and did a profile shift. (gears run smooth)
e.g. 40/20 48DP has 0.625" Center distance and 42/21 Module 0.5 has 0.6201" center distance. Leaves only a small difference.

https://evolventdesign.com/pages/center-distance-calc

Greetings Timo

Thanks Timo. Stamped on the cutters for this particular set besides the angle an range of teeth is .045 is that the depth of the cut?
Harvey

 

[timo_gross]

Thanks Timo. Stamped on the cutters for this particular set besides the angle an range of teeth is .045 is that the depth of the cut?
Harvey

I am a "metric Person" and not Expert. So I do not know. If I calculate 25.4 mm *0.045 = 1.143 mm it seems at least plausible. (assuming 48 DP is what you have there.)
Addendum would be 1x and dedendum 1.16 x the module. I usually go to 1.25 x module for dedendum, so that would be a little deeper. I would test cut a set with 0.045" and see how the center distance "feels", then adjust depth if required.

Good luck.

p.s.

 

[Jasonb]

Some advocate a larger Dedendum for the smaller gear sizes of 1.4 so your 0.045" falls between the two.

https://www.hpcgears.com/pdf_c33/27.48-27.60.pdf

On a model I tend to cut the gears and then use them to set the final ctr distance on the engine with a slip of paper between to allow a little backlash. So you could position the crankshaft holes as drawing and then "depth" the camshaft position to suit

 

[L98fiero]

Upshur Plans call for 20 degree PD gear cutters.
I have the correct cutters, but are for 14.5 degree ptich.
Can I get by with the same gear center distance for an ok mesh, or if not, how much change would I have to due in what direction?

Short answer, changing the pressure angle of a gear does not change the pitch diameter.