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Tangent Relation

The Tangent relation makes a line and a circle or arc, or two circles or arcs, just touch with no kink, and keeps them touching as the sketch changes.

When to Use It

  • Run a straight leg smoothly into a round end
  • Make a belt line touch two pulleys
  • Make one circle rest against another

Step by Step

  1. Open a sketch and draw the pieces (see Lines, Circles and Rectangles). Sketching is part of modeling, which comes with the Pro plans.
  2. Click Select on the Sketch tab (or press S).
  3. Click a line and then a circle or arc (either one first), or click two circles or arcs.
  4. 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 Tangent. Instead of waiting for the bar, you can right-click the selection and choose Tangent under Make them, or click Tangent under Add a relation in the Properties panel.
  5. A small green square marks the relation on the sketch, and a message says Tangent added. It stays true as you move and resize; Edit, Constraints lists it. Ctrl+Z takes it back.

Options

SettingWhat it does
Line and roundThe line and the circle or arc touch at one point. The first piece you pick stays and the other moves.
Two roundsTwo circles, two arcs, or one of each. The second moves along the line between the two centers until they just touch, keeping its size.
Outside or insideSide by side (centers a radius plus a radius apart) or one inside the other (centers a difference of the radii apart). It takes whichever the two are already nearer to when you add it.
Same size, overlappingTwo circles of the same size are always made tangent on the outside.
Listed asTangent.

Tips

  • Drag either piece afterward and the other follows, still touching.
  • If a size is typed for either piece later, they stay touching.
  • To start an arc already tangent to a line, use Tangent Arc.
  • A part edge can be one of the two.

If Something Goes Wrong

  • "Tangent 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.
  • "Tangent 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.
  • "Tangent 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.
  • The bar does not show Tangent. It needs exactly two pieces: a line and a circle or arc, or two circles or arcs.
  • It cannot hold. Tangent is refused when it would fight a relation already there, for example two circles whose centers are tied together.

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