Drawing an Involute Spur Gear (HD)

This video details the process of drawing an involute spur gear by hand in SolidWorks.

[mitselek]

7:18 You got it wrong - "the segment distance between first two points" should actually be "the segment distance of base circle between first two points".
Difference might seem irrelevantly small but actually it makes your profile significantly different from involute gears.

[EricDobsonTV]

This is outstanding, exactly what I was looking for. I knew there had to be a way to draw a proper gear with nothing but geometry and math within the CAD tool being used. So many other tutorials rely on external calculators, spreadsheets, importing coordinates… This is the way.

[bigbattenberg]

Great tutorial. I am reverse engineering some pretty interesting gears from a lathe gearbox - actually there are gears with different numbers of teeth working on the same center distance (slide gears). For example, there's a 30 and a 33 tooth gear, both with the same OD, that work with a 24 tooth counter gear. I have calculated the gears to be DP 12, with a +0.4 profile shift on the 24 tooth gear and yet to be determined positive/ negative profile shift on the 30/ 33. With the given center distance these can be accurately calculated. The SolidWorks modeling is great for checking. I plan to get the actual sample (damaged gear) on a profile projector and get a 1:1 image from that which I then will be able to check against my SW constructed profile. This should be sufficiently accurate. Thanks again for the video.

[The_Engineering_Boost]

For those who need the equations:

1. Pitch Diameter (d) = given (you choose)
2. Number of Teeth (n) = given (you choose)
3. Pressure Angle (p) = given (you choose; typically is 20 deg)
4. Diametric Pitch (dp) = n / d
5. Dedendum Diameter (dd) = d - ( (1/dp) * 2)
6. Adendum Diameter (da) = d + ( (1/dp) * 2)
7. Base Diameter (db) = d * cos(p)
8. Tooth Width (tw) = pi / (2 * dp)
9. Half Tooth Width = tw /2
10. Tooth Width Angle (ta) = (tw / d) * (180 / pi)

Hopefully these are correct. Correct me if I'm wrong. AM 8/26/2020

[ProperParts]

Thank thank you so much. This was so well done and calmly and clearly explained.

[bigbattenberg]

Update: GCSW - Free Gear Calculator from KHK gears - get a DXF output of any gear profile which can be imported in SW to make the gear in 3D. Just did this, works great in no time at all.

[bharat_kachroo]

Thank you Michael. It's a very nice tutorial.

[devinanderson]

I like the information on the involute profile and how to draw it.

What I didn't so much like is modeling practices, especially in SW, So for others learning always mirrors the sketch if you can it is far far more efficient to solve and you're going to be patterning also so it's really important to keep your features light. If he were to do a whole gearbox his system would slow to a crawl trying to solve a mirror pattern on a few thousand features.

also and this is more if you ever plan on working for others give variables names that make sense and if you're going to use a shit ton of construction geometry either name it in the sketch or name them in the variables for a teaching aid I would add the name in the dim text.

lastly, add radios using the feature. you will find that relief radi changes depending on how something is machined it's far easier to change the radius feature named gear relief than to undo a double tangent constraint.

I would have also defined most of the calculated values in the equations but that is just my preference, I would also have put the 3 diameters in their own sketch and described the involute curve in another. I may have been so inclined to put the extrude geometry on top of the theoretical curve just to keep it clean and understandable then there would be an argument to define the relief in the sketch.

[vincentlee]

Did you say The tooth width is 7.85 inches AT VIDEO 14:02 or u meant 0.785? Thanks

[BilletBenny]

I think you're a little off on your involute profile. The variable radius lines should equal the arc length along the base circle and not the line segment between the two points. The error is growing for every sequential radius calculation.

[cruch]

Where does the pressure angle come in or did I miss that part?

[RdelaCourt]

I am trying tp create my involute curve with the following sized gear:

Picth Dia. = 330
Module = 3
No. of teeth = 110
Pressure Angle = 20°

My base circle Diameter (134.67mm) is much smaller than the pitch diameter and also the addendum.

This presents an issue when I create the involute curve connecting the segments. the involute curve does not intercept the pitch diameter.

Has anyone modeled larger gears?

[saviovogt]

Is this how to Create a SolidWorks Part Model of a spur gear using ‘Unwin’s Construction Method? if yes thanks you so much...if no...pls could you direct me to the appropriate video link

[weeklyexposure]

How about when the base diameter is the smallest

[huanhuang]

It's a great job!
I got a question with using lengths of equally segmented lines instead of those of equally segmented arcs to creat the points of involute spline.I know it does not matter that much, for there must exist lengths of arcs equal to those of lines.For someone who cant figure this out, it might bring themselves brain racking how this work how it can be, not in a serious way for some aspects.
Thanks again.Great Job!

[scalor]

Thanks so much for the HD version. Need to learn this manual way to draw a gear based off some old pdf as the automatic methods aren't giving me the exact same result.

[fernandosh]

...There is a possibility of using parametric equation.
X= dbase × cos(t) + dbase × t × sin(t)
Y = dbase × sin(t) - dbase × t × cos(t)

dbase = base diameter
t = angle radians

Good luck.

[The_Engineering_Boost]

why do i get my base circle diameter smaller than my dedendum diameter???

[nowheretosit]

Solidworks is a bizarre program because you can't natively rotate an assembly. Once you draw it on a particular axis, it's there for life.