Overview#
Fusion provides dedicated tools for the closed shapes that appear most often in mechanical design. Each one draws a whole profile in a few clicks and, importantly, builds in the constraints that a hand-drawn version would need. A 2-Point Rectangle arrives with four lines, two horizontal and two vertical constraints, and coincident corners; a slot arrives with tangent arcs and equal-length sides. Using the right tool is faster and gives a more robust sketch than drawing the same outline with lines.
This page covers the Rectangle, Circle, Polygon, Ellipse, and Slot tools, the sub-variants of each, and what each variant is best at.
Where to find it#
All of these are on Sketch > Create and are active only inside a sketch. While a tool is active, you can switch between its types in the Feature Options section of the Sketch Palette.
| Tool | Variants |
|---|---|
| Rectangle | 2-Point, 3-Point, Center |
| Circle | Center Diameter, 2-Point, 3-Point, 2-Tangent, 3-Tangent |
| Polygon | Circumscribed, Inscribed, Edge |
| Ellipse | Single ellipse tool |
| Slot | Center To Center, Overall, Center Point, Three Point Arc, Center Point Arc |
Press S to run any of them by name.
Note: not confirmed in Autodesk's documentation: single-key shortcuts such as R (rectangle) and C (circle). They are common defaults but the sketch help lists only S and D.
Step by step: rectangles#
- Choose Create > Rectangle > 2-Point Rectangle.
- Click the first corner (for example, the origin).
- Either click the opposite corner, or specify the length, width, or both values and then click to place the rectangle.
- Press Enter to complete the tool.
Variants. The 3-Point Rectangle takes a first corner, a second corner (or length value) that sets the length, and a third corner (or width value), so the rectangle can be rotated. The Center Rectangle takes a center point and a corner (or length and width values), which makes the rectangle symmetric about the center. Center rectangles are convenient for plates that sit centered on the origin.
All three create four lines. Each line is an independent entity: if you delete one, the rectangle is just three lines, and the profile opens up.
Step by step: circles#
- Choose Create > Circle > Center Diameter Circle.
- Click the center point (you can snap to construction geometry and points).
- Specify the diameter value, then click to place the circle. Press Enter to complete the tool.
Variants.
| Variant | Inputs | Best for |
|---|---|---|
| Center Diameter | Center, then diameter | Holes, bosses, anything with a known position and size |
| 2-Point | Two points on opposite sides | A circle that must span a known distance |
| 3-Point | Three points on the circumference | A circle through three known points |
| 2-Tangent | Select two lines, then a radius value or a point | A circle touching two lines |
| 3-Tangent | Select three lines | A circle inscribed within three lines |
The tangent variants keep the circle tangent to the selected lines (the docs describe them for lines). You can click lines individually or window-select them. A circle's dimension is a diameter by default; see the dimensions page for dimension options.
Step by step: polygons#
- Open Create > Polygon and choose a variant.
- Click the center point (for Circumscribed and Inscribed) and specify the radius.
- Press Tab to switch from radius to number of sides and enter the count.
- Drag the pointer to orient the polygon, then click to place it.
Variants.
- Circumscribed Polygon: The radius defines a circle that the polygon is circumscribed around: the midpoint of each polygon edge lies on the circle. Use it when you know the across-flats dimension (double the radius), such as a nut or hex key.
- Inscribed Polygon: The radius defines a circle the polygon is inscribed within: the polygon's corner points lie on the circle. Use it for across-corner dimensions.
- Edge Polygon: You place the two points of an edge (length, Tab to angle), specify the number of sides, then drag to orient the polygon to either side of the edge. Use it when the side length is the controlling dimension.
Note: not confirmed in Autodesk's documentation: the default number of sides, the construction circle and constraints created with a polygon, and whether the side count can be edited afterward. Redraw the polygon if you need a different count.
Step by step: ellipses#
- Open Create > Ellipse.
- Click the center point.
- Specify the first axis point: enter its length, press Tab to switch to the angle, then press Enter or click.
- Specify a point along the ellipse by entering the second axis length and pressing Enter, or by clicking.
- Dimension both axes with D.
Ellipses have two axes and a center. Ellipses are useful for oblong holes in design-for-aesthetics, but for most mechanical work a slot is a better choice because it is easier to dimension and manufacture. An ellipse cannot be filleted easily with tangent arcs at predictable points.
Step by step: slots#
Slots are stadium shapes: two parallel sides and two semicircular ends. Fusion offers five slot variants:
| Variant | Inputs | Typical use |
|---|---|---|
| Center to Center Slot | Center of one end, center of the other, then width | The most common method; the end-center distance and width are the design values |
| Overall Slot | One extreme end, the other extreme end, then width | When the total length matters (for example, a slot that must fit inside a 30 mm space) |
| Center Point Slot | A center point of the slot, an end center, then width | Symmetric slots about a known center |
| Three Point Arc Slot | Start, end, and a point on the path arc, then width | Curved slots along a 3-point arc |
| Center Point Arc Slot | Center of arc, start, end, then width | Curved slots on a bolt circle or pivot arc |
In the linear slot tools, you enter the distance and angle between the two points (Tab switches between them) and then the slot width. The Center Point Arc Slot takes the arc center, the distance to one end center, the angle between the two end centers and the width.
Note: not confirmed in Autodesk's documentation: the exact curves and constraints a slot generates (for example a construction centerline, tangents and equal radii). After drawing, inspect the constraint badges and add dimensions for length and width.
Slots suit adjustment slots in plates and key slots. Compared with drawing the outline from lines and arcs, the slot tool needs far fewer clicks and constraints.
Options reference#
| Option | What it does | Notes/default |
|---|---|---|
| 2-Point Rectangle | Two opposite corners, or length and width values | |
| 3-Point Rectangle | Three corners (length, then width) | Can be rotated |
| Center Rectangle | Center point and a corner | Symmetric about the center |
| Center Diameter Circle | Center and diameter | Default circle |
| 2-Point / 3-Point Circle | Circle through two or three points | Points can be existing geometry |
| 2-Tangent / 3-Tangent Circle | Circle tangent to two or three curves | Tangent constraints are created |
| Circumscribed / Inscribed Polygon | Regular polygon around or within a circle | Tab switches from radius to number of sides |
| Edge Polygon | Regular polygon built on a chosen edge | Length, angle, then number of sides |
| Ellipse | Center, first axis point, second axis point | Dimension both axes |
| Slot variants | Stadium shapes, straight or curved | Distance, angle, then width |
| Construction | Makes the shape construction geometry | Linetype > Construction in the Sketch Palette |
Tips and pitfalls#
Tip: Use the Center Rectangle for plates and symmetric parts. A center rectangle on the origin dimensioned with two numbers is a quick way to build a symmetric plate; check the constraint badges to confirm it stays centered.
Tip: Draw a hexagon with the Circumscribed Polygon when you know the wrench size (across flats). With the Inscribed variant you would need to compute the corner distance first.
Tip: Use a slot instead of two circles plus a rectangle plus trimming. It is fewer clicks.
Warning: A rectangle is four independent lines. If you drag a single corner when the rectangle is not fully constrained, it deforms; always dimension a rectangle or apply constraints before assuming it is rigid.
Warning: The rectangle variants may carry different constraints. Check the badges rather than assuming.
Warning: Tangent circles have more than one possible position. Move the pointer to the side where you want the circle before clicking.
Practice exercise#
- Sketch on the XY plane. Draw a Center Rectangle on the origin and dimension it 80 by 50 mm.
- Add a Center to Center Slot inside, with its start 20 mm left of the origin and its end 20 mm right, 8 mm wide. Constrain the slot so its centers are horizontal and its midpoint is on the origin (use Horizontal/Vertical with Midpoint or Symmetry constraints).
- Draw a Circumscribed Polygon with 6 sides above the slot with an across-flats distance of 10 mm.
- Add a 2-Tangent circle that touches the rectangle's two top corners' adjacent lines (a corner-fitted circle) with a radius of 6 mm.
- Extrude the plate profile 4 mm.
Expected result: a symmetric plate with a slot, hex pocket, and corner circle, all fully defined and turning black.
Related#
- Lines, arcs, and points (02-sketching/lines-and-arcs)
- Constraints (02-sketching/constraints)
- Dimensions (02-sketching/dimensions)
- Trim, extend, fillet, offset, and patterns (02-sketching/modify-tools)