### Snap points on an arc

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### Snap points on an arc

#81613 by GLanguell
Wed Oct 12, 2022 4:41 pm
I am trying to design a cone template for a shop project, I need to be able to divide an Arc by a certain distance along the arc. I thought about using the divide command or using snap points, but I'm not seeing how to make that work. I don't want to just divide the arc by X amount of divisions. I ended up creating two arcs to create the cone, then printed it to 1/4 scale, broke out the old trusty compass and marked off the 6-secgments I needed. After that I found the angle at the end of the 6th segment. Went back in to DataCAD and dropped a line to match the paper sketch. It works, but I have to believe DC has the power to do this!

I'm all ears and in full learn mode!!

The measurements of the cone I am trying to draw are:

Top opening = 6"
Bottom Opening = 10"
The Hypotenuse measurement is 5"

I'm happy to share the drawing that I have completed so far.
Many thanks!
Gene Languell
GLanguell@msn.com
260-437-2849 Cell

### Re: Snap points on an arc

#81615 by Nick Pyner
Wed Oct 12, 2022 9:05 pm
If, by hypoteneuse, I understand correctly that you are measuring along the side of the cone, that's a pretty unfair way to do it in DCad, but it is doable.

### Re: Snap points on an arc

#81617 by dhs
Thu Oct 13, 2022 5:28 am
Hi Gene,
I understood your question differently to Nick. If neither of us has properly understood you question then some clarification may be useful on your part (or sharing the drawing).

I thought you were looking for the angle for an arc that contained 6 chords of a specific length? ... if that is the case then you could do in DataCAD what you did on paper, i.e. draw a temp circle of the required chord length centered at one end of your arc - the other end of the required chord would be the intersection of the circle with your arc (you could repeat the process 6 time as you did on paper, or simply measure the resulting angle and multiply it by 6).
I personally would use a calculator to work this out using the following formula to find the angle of a single chord (i.e multiply by 6 if you want the angle for 6 chords):
Angle of chord = 2 x arcsine( (chord length / 2) / radius)
I've put the calculation in the attached spreadsheet ...

### Re: Snap points on an arc

#81620 by GLanguell
Thu Oct 13, 2022 10:02 am
I lost some sleep last night but I ended figuring it out. I decided to go back to my EE geometry books and see if I could figure it out mathematically. I got close, within 1/8" to 1/16" but I could get the arc length to equal 5.0" exactly. Then I stumbled up the Cent. Chord. function in the Curves menu. That was EXCETLY what I was looking for! Pick the Arc Starting point, Then Pick the Arc Center, then ENTER THE ARC LENGTH! WHA-LA! That's exactly what I needed! From there it was finding out the angle and rotating a line around the arc until I had all six segments.

Attached is the drawing. I also found a good youtube video explaining how to make a cone in under a minute!

Thanks EVERYONE for the help!

Gene
##### Attachments
How to Create a Cone Pattern

### Re: Snap points on an arc

#81622 by dhs
Thu Oct 13, 2022 1:33 pm
Gene,
Glad you managed to find the best solution - I didn't notice the Cent. Chord option. Probably easier than doing the math outside of DataCAD.
Just wanted to check that the drawing you attached is the latest where you used the Cent. Chord option though? - I measured the the chord in your drawing at 4 31/32 (but when I use Cent. Chord with radius of 1.0.19 and length of 0.5 I do get exact result):
Chord Length.png (16.3 KiB) Viewed 2521 times

Regards,
David H.

### Re: Snap points on an arc

#81623 by Nick Pyner
Thu Oct 13, 2022 7:19 pm
dhs wrote:Hi Gene,
I understood your question differently to Nick. ...

I didn't really understand it at all.... I just wanted to get a starting point for making up a truncated cone.
I assumed the geometry/divide button would get some work - eventually

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