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I have a worm gear set with no drawings. I need to model them. The only things I know are 1) The Gear ratio is 30, and the worm gear only has one thread. It is a single start as opposed to a multi start worm. 2) The diameter of the worm is 0.7 Inches, and the length of the worm is 0.852 Inch 3) The diameter of the gear is 1.007 Inches, and it has 30 teeth.

I do not know the pressure angle, diametrical pitch or gear module.

What other piece of missing information would I need to know? How do I go about figuring out the diametrical pitch? How do I figure out the module.

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  • $\begingroup$ If you have the physical parts, why not just measure them? $\endgroup$ – Jonathan R Swift Apr 14 '20 at 9:13
  • $\begingroup$ All I have to measure with is a micrometer. I can't measure the pressure angle or diametrical pitch with that. $\endgroup$ – user77232 Apr 14 '20 at 12:32
  • $\begingroup$ What about a camera? (or better, a flatbed scanner). You can measure a huge number of things optically. $\endgroup$ – Jonathan R Swift Apr 14 '20 at 14:08
  • $\begingroup$ If using a camera take the photo from as far way as possible (zoom in if you have a lens that allows you to), to eliminate paralax etc. Take the photo against a known grid so you can adjust for perspective. $\endgroup$ – Jonathan R Swift Apr 14 '20 at 14:09
  • $\begingroup$ Nope, I don't have a camera with a zoom lens or a large enough aperture to take a simulated telecentric photo of the part. $\endgroup$ – user77232 Apr 14 '20 at 15:00
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Lets say to make it simple you have the disk with 30 teeth. So the distance between each is 1.07 *pi /30= P

Now your worm circumfrance is 0.7pi. We know the slope of the thread on the worm should be such that 30P = 0.7pi.

Dividing by 30 we get P = 0.7pi/30. This is the slope of the thread on the worm.

30 turns on the worm will turn the disk 30 teeth or one turn.

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