Unit 03 · Lecture 7
Curved disk: Project Geometry and cylinder cuts
This part looks like the previous curve part, but adds an angled base and a cylinder with slots cut into it. You will sketch on a model face for the first time and use Project Geometry to reuse existing edges.
Video 15:20Reading 8 minUpdated 26 October 2026
What you will build
A 10 mm base with an angled edge, a curved slot, three M10 × 1.5 holes and a Ø30 centre hole, plus a Ø50 cylinder 30 mm tall with three 20 mm slots cut 10 mm deep.
You will learn
- Finding a centre point from its two leader lines
- Aligned dimensions for angled measurements
- Starting a sketch on a model face
- Project Geometry
- Extrude in Cut mode, with a pattern
Before you start
Build the curve part first. You will reuse its slot and circular pattern methods.
Step by step
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01
Anchor at the main circle’s centre
0:42This part has no convenient corner, so put the centre of the big circle on the origin. Sketch on XZ and draw circles of Ø90, Ø160 (R80), Ø40 (R20), Ø60 (R30) and Ø20 (R10).
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02
Constrain with tangents and leader lines
2:02Make the circles tangent to their neighbours. To place a centre, look for the two leader lines that come out of it. The R20 centre is 78 mm horizontally and 40 mm vertically from the origin. The R30 centre is 88 mm and 20 mm.
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03
Close the base
3:24Draw the bottom line long and away from the circles, make it tangent to both, then trim.
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04
Build the slot
4:08Number the slot circles 1–5. Circle 1 is Ø30, circles 3 and 4 are Ø16 (R8), and the outer arc is Ø90 (R45), 22 mm above the origin and placed by tangency.
The line joining circles 3 and 4 is parallel to the angled base and 16 mm from it.
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05
Use an aligned dimension
6:58The 15.5 mm spacing is measured along the slant. While placing the dimension, right-click and choose Aligned. That gives the shortest distance between the two points, not a horizontal or vertical one.
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06
Holes and base extrusion
8:24Add a Ø20 circle, then a Ø10 hole 35 mm above the origin. Circular pattern it 3 × 360°. Add the Ø30 centre hole and extrude the base 10 mm.
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07
Sketch on the face and project its edge
10:38Click the top face and choose Create Sketch. Draw a Ø50 circle. On its own it is a solid disc, so you also need the inner hole. Instead of drawing it again, use Project Geometry and click the Ø30 edge. It copies onto the sketch and stays linked. Extrude the ring 30 mm.
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08
Cut the slots
11:58Sketch on top of the cylinder. Draw a Two Point Center rectangle 20 mm wide, vertically aligned, with its centre 20 mm from the middle. Circular pattern it 3 × 360°. Extrude with output set to Cut and a depth of 10 mm. Finish with a 2 mm chamfer, 0.5 mm hole chamfers and M10 × 1.5 threads.
Key ideas
Project Geometry
Projecting takes an existing edge and places a linked copy on the current sketch plane. If the original edge changes, the projection follows. Use it whenever a new sketch must line up with geometry you already have.
Join vs. Cut
The Extrude output decides what happens to the material. Join adds it to the body, as with the cylinder. Cut removes it, as with the slots. The same sketch can be used for either.
Common mistakes
- Using a horizontal dimension for a slanted 15.5 mm value. Switch to Aligned.
- Trying to sketch on the curved cylinder side. Sketches need a flat face or plane.
- Leaving the extrude output on Join when cutting the slots.
Practice exercise
Change the cylinder to Ø60 and the slots to 4 × 90°. Check that the projected Ø30 hole stays in place.
Check yourself
A dimension runs parallel to a slanted edge. Which dimension type?
Aligned.
What does Project Geometry give you on a new sketch?
A linked copy of an existing model edge.
Which Extrude output removes material?
Cut.
How do you find where a centre point goes?
Follow its two leader lines, one horizontal and one vertical dimension.
Want the graded version? Take the 5-question lesson quiz in the course player after the video.
Written by the CADsmit instructor from the lecture recording and checked in Autodesk Inventor Professional 2027. Last updated 26 October 2026. Spotted an error? Tell us.