Create a Plane tangent to cylinder

jeffrey_mackniak

I cant seem to figure out how to place a plane tangent to cylinder.
I am trying to place a .50 hole .25 deep on the main body of this model train for the smoke stack
https://cad.onshape.com/documents/0f13410bf0c253e8bbb0896c/w/9625ef0b3f7cfcac49c6afec/e/39e970c0ad022d35c10a5792

Prachi

I like to use mate connectors for holes as it lets me select several locations at once all tangent to the surface. It's another option than creating normal planes for each location. Locations are mate connectors at the end of each line.



https://cad.onshape.com/documents/d40e5dfa55dd72b1ed0a3d33/w/4fc50795429279f1225e8524/e/97ec5ecf413827b8b7fb44d5

alnis

Edit: Oops! I wrote this as @glen_dewsbury replied and didn't see his response. Sorry for the double post!

There are a few ways to approach this. I made a copy of the model with some possible solutions. I'm sure there are also other ways to do it.
https://cad.onshape.com/documents/c66a015ad5d912ab32c65709/w/05eb2641e84c5b48bff181e8/e/618e9ae0e41e30a079ea4fa6

1. Use the tangent plane custom feature with the cylinder and the top plane (probably what you're looking for)
2. Make a sketch using an implicit mate connector offset from the end of the cylinder, then revolve (works well in weird orientations)
3. Use a midplane for the cylinder, then revolve the sketch (simplest)

As a side note, I recommend making your model symmetric about as many planes as possible right from the get-go to make these sorts of operations easier. Rather than having to construct midplanes and use dimensions, it will be easier to use symmetric extrudes, and your mirrors/sketches/etc. will be a lot cleaner. Here's where I would probably have modeled this part if I were to do it from scratch:
https://cad.onshape.com/documents/c66a015ad5d912ab32c65709/w/05eb2641e84c5b48bff181e8/e/c6ea5337d2b4fe63b118692f


There's also a great video that I know of for best practices when starting a new CAD model (it's for Inventor, but most of it applies to Onshape), but I'm having trouble finding it at the moment. I'll reply here if I do find it.

steve_shubin

@jeffrey_mackniak

Here is another way to do it

1. EDIT Sketch 3 — add a point at the apex of the arc
2. Now make your plane using the PLANE POINT type

loic_gaulin

All of these answers helped me, but I took them and found a slightly different way because I have non-cardinal orientations.  I started with Prachi's mate connectors and was able to get that to work, but it took longer than I wanted to repeat over and over due to having to orient and move each connector.  I then took Steve's idea and ran with it.  

By making a sketch that has the curve I need planes tangent to, that has radii lines at the appropriate locations, I was able to create a line tangent to the curve (using the tangent constraint and starting the line where the radius line meets the curve) at the required locations.  Using the "line angle" plane, it was a simple matter of picking the correct line and setting the angle to get the plane tangent to the curve (here i had to rotate by 90, but the first two required no modification).