Cutting negative space from solid object

Hi,
New to SketchUp, have been working on this piece for a couple of days on and off. I have watched some YouTube videos to try and figure out what my issue is.

I am modeling a block that has a 7 degree face on one side. I want to cut holes through it, and partial holes (think countersunk holes). Some of the holes are perpendicular to the “in plane” surface and some are perpendicular to the 7 deg surface. I can’t seem to figure out how to “cut” the holes out.

I am also trying to round the edges of the block, but again due to the 7 deg face, I can’t round the entire corner… I get this:


I have attached my model. Any guidance is welcome. I am new so just learning. Thanks.
Brake adapter R3.skp (131.7 KB)

There’s a bunch of things here that need fixing but first a question. Are there supposed to be bosses around the corner holes as you have them? Or are those counterbores. You mention countersinks but I don’t see any in your model.

Is this what you are trying to end up with?

This is my interpretation of what you have in your model.

I started by outlining the object on the ground plane with the radiused corners and the through holes.


Then I pulled the face up to the bottom of the lower counterbores and drew in their perimeters.

Pulled up to the height of the other counterbores and drew them in.

After that I extruded the thing up a little beyond the required height and drew in a rectangle at the right height and rotated to the required angle.


After selecting all of the geometry I used Intersect Faces>With Selection and then erased the waste geometry. The extra length on the extrusion made it simple to select everything above the angled face to delete it.

For the central hole I drew it on the top face and pushed it well past the bottom face.


Then select the cylinder wall and the bottom face, choose Intersect Faces>With Sellection followed by erasing the waste.

An important thing about drawing the circles is to make sure you are dragging out the radii on axis and not in some random direction. There’s no need to draw the circle for the hole on the bottom face, either.

Note how the certices on your circles are randomly located relative to the axes.


Compared to this:

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Yes, wow you nailed it. This is my 3rd attempt and it looks like I just don’t understand the fundamentals of the program. I first sketched the block without the 7 deg angle, then tried to a “triangle” on top: Fail. 2nd I tried to draw the block then stretch one side with the scale tool, that was also a massive failure… it added all kinds of little triangles in 3D space, I assume that’s due to my not stretching in one of the planes. Any way, yes you have done essentially what I am looking for. Now, you said “There’s a bunch of things that need fixing…” Can you elaborate? I’m 3 days in and learning by trial and error, feels more like trial by fire. Thank you for all of the help BTW.

You should probably stop on this project to learn the fundamentals at learn.sketchup.com and then come back to it.

Well, I mentioned several things already. Drawing circles on axis is incredibly important. Also doing things in the correct order makes the process easier. Like creating the radiused corners while the thing is still 2D saves you a ton of work later. A lot of this stuff comes with practice as you learn to correctly use the tools. It’s like learning to almost anything else. You have to know what the tools can do and when its appropriate to use them.

How are you going to use this mode once it is finished?

FWIW, I did try to use the Intersect Faces with Selection and I get an error “No intersections found between selection set and the rest of the model.” Why am I getting this error? Idk, I did it the same way you are showing.

This is a adapter for a brake master cylinder on a classic car. I am putting a newer model master cylinder in the car and it needs an angled mount for the firewall. My plan was to have a friend 3D print it for proof of concept then take it to a machine shop for milling out of aluminum. Overkill for a machine shop? Probably, but I wanted to try it out.

I would have to guess you didn’t do it exactly the same way or you wouldn’t have gotten that message. Did you have all of the face selected before using Intersect Faces?

Seems like a good idea to 3D print a proof of concept before having the thing machined from aluminum.

I would say that’s an excellent example of good use for 3D printing.
Proof of concept and rapid prototyping is where it shines!

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