12.2 Coincident, Concentric, Parallel, Perpendicular

12.2 Coincident, Concentric, Parallel, Perpendicular

Quick Answer: Open Mate, select two valid entities (faces, edges, axes, planes…), choose a standard mate type, set Aligned or Anti-Aligned, and accept. Coincident + Concentric place most shafts and covers; Parallel and Perpendicular lock directions when contact alone is not enough. Always drag-test after a mate group.

SOLIDWORKS’s standard mate set used on CSWA includes Coincident, Concentric, Parallel, Perpendicular, Tangent, Distance, and Angle, with Aligned / Anti-Aligned control on many types. This section drills the four directional/position mates you apply constantly; Distance, Angle, and Tangent follow in 12.3, and DOF diagnostics in 12.4.

Mate PropertyManager workflow (memorize)

1. Insert → Mate (or Mate toolbar / context Mate).
2. Select geometry on component A, then component B (order rarely matters; entity type does).
3. SOLIDWORKS proposes a mate type—verify it matches intent; change type if the auto-guess is wrong.
4. Set alignment: Aligned vs Anti-Aligned (flip) until the preview matches the isometric/drawing.
5. Click ✓ / Add/OK to commit.
6. Drag the free component. Remaining motion should match the real mechanism (or no motion if fully constrained).

Valid selection cheat sheet

Trap: Selecting a fillet face when you meant the planar pad face, or selecting the hole edge circle when you needed the cylindrical hole face for concentric. Wrong topology → wrong or failed mate.

Coincident mate

Coincident forces selected entities to occupy the same place (faces share a plane of contact, points share a location, etc.).

Exam uses

• Seat a cover flat on a base top face
• Align a bracket face to a plate face
• Put a vertex on a plane (less common but valid)
• Mate a component plane to an assembly plane for orientation

Coincident vs Distance(0)

Coincident is the clean “touching / coplanar” mate. A Distance mate of 0 can look similar but is a different feature—prefer true Coincident when the drawing shows flush contact with no gap callout. Reserve Distance for nonzero clearances (12.3).

Alignment flip on faces

Face-to-face coincident can land outside (normals opposed wrong for your intent) or inside. Use Anti-Aligned / Aligned so the component sits on the correct side of the face. If the bracket appears buried in the plate, flip alignment before adding more mates.

Concentric mate

Concentric forces axes of cylindrical (or conical) geometry to coincide—the classic shaft through hole mate.

Exam pattern: shaft + hole + face seat

Most CSWA shaft assemblies use a two-mate kit:

1. Concentric — cylindrical shaft face ↔ cylindrical hole face (or axes).
2. Coincident — shaft shoulder face ↔ housing face (or similar axial stop).

That pair removes the major freedoms that would leave the shaft spinning in space or sliding forever. A third mate (Plane parallel, Angle, or another coincident) may finish rotation if the design is not free to spin.

You do not need to memorize exact DOF arithmetic for every combo under fire, but you do need to drag-test: after concentric+coincident, the shaft might still rotate—that can be correct for a pin. If the drawing shows a keyed fixed orientation, add the mate that stops rotation.

Concentric selection tips

• Prefer cylindrical faces (easy to see).
• Temporary axes work if faces are hard to pick (Right-click → Select Mid / show temporary axes).
• Concentric on wrong diameter features (outer boss vs inner hole) still “succeeds” geometrically but places the part incorrectly—watch the preview.

Parallel mate

Parallel keeps two entities’ directions the same without forcing them to touch. Faces stay parallel; a gap may remain.

Exam uses

• Keep a slot’s sides parallel to a base edge while another mate sets position
• Orient a bracket so its face stays parallel to a plate when coincident on another face already sets contact elsewhere
• Prevent unwanted tilt when only concentric is applied on a long part

Parallel is not Coincident. Parallel alone does not pull faces together. If the drawing shows flush contact, you need Coincident (or Distance 0 carefully), not only Parallel.

Perpendicular mate

Perpendicular forces a 90° relationship between selected entities (for example, two planar faces, or an edge and a face).

Exam uses

• Square a plate edge to a base face when geometry is not already orthogonal from other mates
• Enforce “upright” orientation after concentric leaves a spin DOF
• Match drawing callouts that show perpendicularity without a third solid face to coincide to

Like Parallel, Perpendicular primarily fixes orientation, not a contact distance. Combine with Coincident/Concentric for full placement.

Aligned vs Anti-Aligned (flip)

Many mates expose alignment:

Exam habit: If the isometric shows the arm on the left and your mate puts it on the right, flip alignment before inventing new mates. Adding a conflicting coincident to “push” it over often creates mate errors or over-definition.

Standard mate error recovery

Do not panic-delete the base Fix. Fix is your ground. Delete recent mates in reverse order while watching the tree.

Worked mini-scenario

Assembly: Base (fixed), vertical plate with Ø10 hole, pin Ø10 with shoulder.

1. Concentric: pin cylinder ↔ hole cylinder. Preview: pin axis through hole; still slides and spins.
2. Coincident: pin shoulder face ↔ plate front face. Preview: seated depth; may still spin.
3. If the head has a flat that must stay horizontal: Parallel or Coincident between flat and Top plane / base top—choose what matches the drawing.
4. Drag pin: no translation; rotation only if intended.
5. Mass Properties when all parts constrained per stem.

Strategy under the 30-point clock

• Mate major location pairs first (concentric+coincident kits).
• Use Parallel/Perpendicular to kill wrong tilt before stacking Distance/Angle modifications.
• After every 1–2 mates, drag-test once—cheaper than diagnosing ten mates at the end.
• Keep the Mate popup open and add multiple mates in one session when efficient, but still verify each preview.

Master these four mates and the Aligned/Anti-Aligned flip, and most CSWA assembly geometry becomes a repeatable pattern rather than trial-and-error. Distance, Angle, and Tangent (12.3) then handle clearances, orientations with numeric values, and curved contact.