# Thread: How to 2D Draw A Tooth of Gear?

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Next draw this cyan (blue) arc and yellow arc.
The centers of these arcs are on the red circle.
There is a bit of a trick to locating the center points - post back if you don't know the trick.

involute.jpg

Post your file here when you have finished this step.

2. Originally Posted by JD Mather
Next draw this cyan (blue) arc and yellow arc.
The centers of these arcs are on the red circle.
There is a bit of a trick to locating the center points - post back if you don't know the trick.

Attachment 39374

Post your file here when you have finished this step.
I don't know the trick.

3. The trick is to simply draw a circle with the desired radius (in this case big_R or r.2675) with the center at a location that you do know. Where that circle passes through the reference circle is one of two possible locations for the desired centerpoint. The one of the two possible points you need is visually obvious.

Center Trick.PNG draw second yellow arc at rightmost intersection of yellow arc shown and red arc. Delete the original yellow circle and trim the second yellow circle beween the pitch circle and the addendum circle as shown in my earlier post.
Repeat for little_r

4. Originally Posted by JD Mather
The trick is to simply draw a circle with the desired radius (in this case big_R or r.2675) with the center at a location that you do know. Where that circle passes through the reference circle is one of two possible locations for the desired centerpoint. The one of the two possible points you need is visually obvious.

Attachment 39378 draw second yellow arc at rightmost intersection of yellow arc shown and red arc. Delete the original yellow circle and trim the second yellow circle beween the pitch circle and the addendum circle as shown in my earlier post.
Repeat for little_r
This is my gear in the attached .dwg file.

Why the shape of the tooth is different compared to the attached image?

5. Where is its epicycloid and the hypocycloid?

6. Where did that come from.
I didn't instruct you to do that?

I guess I didn't write it exactly like that, but
Are you willing to work through the entire process - beginning to end (read, not so easy)?
I was walking you to the solution step-by-step. You missed my last step.
Post file that looks like #13.

7. Originally Posted by JD Mather
Where did that come from.
I didn't instruct you to do that?

I guess I didn't right it exactly like that, but

I was walking you to the solution step-by-step. You missed my last step.
Post file that looks like #13.
I thought that was the last step.

I will post the .dwg file that looks like #13.

8. Got to pay attention in class.

9. This is the .dwg file that looks like #13.

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Now draw circle with center at intersection of yellow circle and red circle as shown.

Big_R.PNG

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