Concentric Relation
The Concentric relation gives two or more circles or arcs the same center, and keeps them that way. It is also the way to drop a point onto the center of a circle or arc.
When to Use It
- Draw a bolt circle and its clearance ring around one center
- Keep a counterbore centered on its hole
- Put a point at the center of a round
Step by Step
- Open a sketch and draw the pieces (see Lines, Circles and Rectangles). Sketching is part of modeling, which comes with the Pro plans.
- Click Select on the Sketch tab (or press S).
- Click a circle or arc, then click each circle or arc that should share its center.
- Keep the pointer still for about half a second. A bar titled Add a relation to the N selected opens beside it, with one button for each relation that fits. Click Concentric. Instead of waiting for the bar, you can right-click the selection and choose Concentric under Make them, or click Concentric under Add a relation in the Properties panel.
- A small green square marks the relation on the sketch, and a message says Concentric added. It stays true as you move and resize; Edit, Constraints lists it. Ctrl+Z takes it back.
Options
| Setting | What it does |
|---|---|
| Circles and arcs | Two or more. The ones after the first move so their center sits on the first one's center. A whole circle moves; an arc moves as a whole. Sizes do not change. |
| A point and a circle or arc | Pick the point (click its dot) and then the round. Concentric puts the point at the center. The other choice in the bar, Coincident, puts the point on the edge instead (see Point on Circle Relation). |
| Which one gives | The held piece stays and the other moves (see The Anchor Rule on the Relations page). |
| Listed as | Concentric for rounds. A point tied to a center is listed as Coincident. |
Tips
- Concentric does not make the sizes equal. Add Equal Relation for that, or give each its own diameter.
- To pick a circle's center point, move the pointer over the circle in Select until its dots show, then click the center dot.
- A part edge that is a circle (a hole in the part) can be one of the rounds.
If Something Goes Wrong
- "Concentric cannot hold together with the relations already there. Nothing changed." Something already placed (another relation, a typed size or a Fix) fights this one. Delete the one in the way from the list under Edit (see Edit Menu) and try again.
- "Concentric already holds through the relations you have, so nothing was added." The sketch already forces this, so nothing more is needed.
- The button is not in the bar. The bar only lists relations that fit what you picked. Check what is selected in the Selected list of the Properties panel. If the panel says None fits this selection. Pick another point, piece or part edge with it., change the picks.
- "Concentric applied once: the relation solver could not load, so it will not be kept." The piece moved once but nothing was stored. Check your connection and add it again.