# Problem With Making Spline Tangent to Circle
**URL:** https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710
**Category:** Modeling Questions
**Created:** [November 10, 2020, 3:30pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710 "2020-11-10T15:30:57Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@henrydmayne](https://discourse.shapr3d.com/u/henrydmayne)
#### Post date: [November 10, 2020, 3:30pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/1 "2020-11-10T15:30:57Z")
I am trying to design a custom cam using a an inner and outer circle, and a spline to draw the curves between them. It is crucial that the two circles remain at a fixed diameter, and that the spline is tangent to the circle where they connect. I have tried using the tangent tool as well as editing the angle between the circle and the spline, but no matter what I do, Shapr3D will make the diameter of the inner circle smaller to match the spline. In Solidworks (which is what I normally use) I am able to select the circle and the spline, and when I make them tangent, the spline curve is changed automatically to fit tangent to the circle. Is there a way to achieve this in Shapr3D, as I would like to use my new IPad to design cam systems, and it is crucial that I know how to do this.
---
### Author:  [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [November 10, 2020, 3:34pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/2 "2020-11-10T15:34:23Z")
Select the circle, and set the radius to the fixed value. Then radius will be locked.
---
### Author:  [@henrydmayne](https://discourse.shapr3d.com/u/henrydmayne)
#### Post date: [November 10, 2020, 3:51pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/3 "2020-11-10T15:51:57Z")
Thanks for the quick reply, I tried making the circle radii fixed, then tried selecting the inner circle and spline to make them tangent, but it only translated the spline and outer circle to be tangent. Please see the attached screenshot.
---
### Author:  [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [November 10, 2020, 3:55pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/4 "2020-11-10T15:55:29Z")
The end point of the spline and the circle are not connected. Drag the end point of the spline to the end point of the circle.
---
### Author:  [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [November 10, 2020, 3:59pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/5 "2020-11-10T15:59:41Z")
I am not sure though that this will work with a single tangent constraint, because you are connecting the same curves in both ends. Probably simply setting the angle between the two curves to 180 is a better idea.
---
### Author:  [@henrydmayne](https://discourse.shapr3d.com/u/henrydmayne)
#### Post date: [November 10, 2020, 4:11pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/6 "2020-11-10T16:11:03Z")
I set the 3 points that I want to have fixed along the spline as well as fixed the radius of the circles, and when I try to make tangent, or set the angle to 180, it doesn’t allow me to. I also made sure the spline endpoints were connected to the circle endpoints. Please see the attached screenshot.
---
### Author:  [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [November 10, 2020, 4:23pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/7 "2020-11-10T16:23:56Z")
I think it’s because the end points of the arc are locked.
---
### Author:  [@henrydmayne](https://discourse.shapr3d.com/u/henrydmayne)
#### Post date: [November 10, 2020, 4:46pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/8 "2020-11-10T16:46:48Z")
I finally got it, I unlocked the endpoints of the circle and fixed the center of the inner circle, and made them tangent. Thank you very much for your quick replies and good service, you’re running a great app!
---
### Author:  [@Istvan](https://discourse.shapr3d.com/u/Istvan)
#### Post date: [November 10, 2020, 4:48pm UTC](https://discourse.shapr3d.com/t/problem-with-making-spline-tangent-to-circle/9710/9 "2020-11-10T16:48:43Z")
Always happy to help 🙂