Lines or arcs drawn around a cylinder.

[Michael Adelong]

Help!

I'm having a hard time trying to draw lines and arcs around the surfaces of cylinders. Is there a keyboard shortcut that helps constrain the lines to the surface?

Thanks,
Michael

[Dave Richards]

Michael, could you post a JPG of what you're trying to do? I'll be able to give you a method if I can see exactly what you're trying to accomplish.

[Michael Adelong]

I was trying to draw the attached object... As you can see, I figured it out. Drawing an arc 1/2 way around the cylinder at an angle is tough.

It was easier to draw a line across the front, copy the existing arc, and then paste it where I wanted it. Tilting it into place was easy after that...

BTW: Sketchup is awesome. I'm just about to be able to draw whatever I want. This is dangerous. Up until now, my mottos have always been:

"If I can see a drawing of it, I can build it." and... "I can't draw a straight line with a ruler."

SU to the rescue!

[Dave Richards]

Michael, Take look at the attached SKP. I copied your cylinder and then drew two cutting planes. After drawing them I selected them, right clicked and selected Intersect with model from the context menu. I stopped there to make it so you could see what it looks like at that point. The next step would be to delete the unwanted geometry.

The drawing here shows a similar use of a cutting plane to miter a molding. Notice the difference between steps two and three. Step two is before Intersect with model while step three is after it.


FWIW, cutting geomtery doesn't have to be flat surfaces. They could be a path followed by a bandsaw blade. It could be a cylinder tilted to a low angle to represent a pocket screw hole. It could also be a tenon on one piece cutting for a mortise on another piece or dovetail pin cutting a socket.

Does that make any sense?

[Michael Adelong]

Thanks, Dave.

I see exactly what you did, but I'm having a problem duplicating it. You refer to drawing "cutting planes". All I can find is the "section plane" tool. I tried inserting a section plane, and then drawing a rectangle on it. I'm pretty close to what you have, except that the rectangle won't "attach" itself to the surface of the plane.

What am I missing?

Michael

[Dave Richards]

You're missing Intersect with model. The cutting plane is not the same as a section plane. The Section plane tool allows toy to make a cut away view. By cutting plane, I'm talking about drawing a plane that cuts through the geometry--your cylinder in this case--and then intersecting it with the geometry.

Think about your cylinder in wood. How would you cut that with a saw blade? draw the cut the saw blade would make, select the cutting plane(s), right click and click on Intersect with model.

[Michael Adelong]

Got it. Thank you.

I thought the "cutting plane" was a tool, not something that you create yourself by making a rectangle and sliding it into place.

Learned 2 ways to do this yesterday. It was a good SU day.

Michael

[Dave Richards]

Michael, glad you got the details worked out. Sorry if I didn't make myself clear initially.