Picking up an Intersection with a Sketch Plane

nick_hanigan

I wish to sketch at an offset of a set distance (0.8mm) into a curved object (a rounded tablet).  I can set up the sketch plane A.O.K, however next I wanted to find the intersecting faces of the curved edges to pick up and create an new extrusion face.  I am not sure how to 'pick these up' to create the sketch references, noting the 'U' Use command seems to be suitable for entity extremities not part way intersects - nor does the intersect obviously allow me to click to select.

I find if I navigate to the new face out of sketch mode, I am suitably able to select the edges to form a completed loop, however this doesn't seem useful as when I switch to sketch mode, those selections are lost.

If someone could point me in the right direction, that would be really appreciated.  NH. 

tim_hess427

I'm not sure exactly what you're trying to accomplish. If you can make the document public and share a link here, it'll be easier for someone to jump in and give more specific advice.

It sounds like you're on the right track with using the "intersect" command. However, I believe the intersect command requires you to select a face or surface, rather than an edge. It then creates lines/curves on your sketch plane where that face intersects the plane. 

https://cad.onshape.com/help/Content/sketch-tools-intersection.htm

xphilip

Too hard to discern the ask to provide meaningful solutions. Is there an example you could build and share?
Sounds doable, but the solution will be dependant on more info.
Share!

nick_hanigan

@tim_hess427 & @xphilip
Thank you both.  What you said was enough to turn my head in the right direction.  I appreciate your support.  Nick.

john_mcclary

It sounds like you want to define a point that lies on an intersection of a plane and "anything"

I usually just create a sketch on the offset plane, then draw a point. then make it coincident, or pierce, etc.. to define the 3D point of intersection.

Here you can see I created planes on the axis of the helix
then created a sketch point that is coincident to the bottom edge of the part (blue line)
then measured 2" up from there to sketch a hole, which is then extrude - cut. (red line)