Is a ʼCoincident Mateʼ the most common way to join faces in SolidWorks?

Short Answer

Yes — in SolidWorks, a Coincident Mate is the most common professional way to join planar or flat faces in assemblies because it quickly aligns faces to touch with no gap. It is fast, stable, and standard in everyday assembly workflows. Limitation: it does not control rotation by itself.

What You Need to Know Before

Warning: A Coincident Mate can make parts touch, but it may still leave unwanted rotational freedom or overdefine the assembly if other mates already control the same geometry. This is especially common when mating symmetric or cylindrical components without a secondary orientation mate.

How to Join Faces in SolidWorks

• Command: Mate

• Shortcut: [Alt, drag for SmartMates]

• Quick Steps:

  1. In the Assembly tab CommandManager, click Mate, or use right-click on a face and choose Mate.
  2. Select the first face, then select the matching face on the other part.
  3. In the Mate PropertyManager, choose Coincident under Standard Mates, verify Aligned/Anti-Aligned if needed, then click the green check.

Variables & Settings

• Key Setting: Lock rotation (available in relevant mate conditions and concentric workflows)

• Expert Setting: If the joined faces still allow spinning or ambiguous movement, use an additional mate or enable Lock rotation where applicable to fully control part orientation and reduce assembly instability.

Why it Fails

• Cause 1 (Geometry): The selected faces are incompatible for the intended mate result, or one face is curved when a simple face-to-face coincident condition is not appropriate.
• Cause 2 (layers/Locks): One component is Fixed or constrained by existing mates, preventing the new Coincident Mate from solving correctly.
• Cause 3 (Command/Logic): A Coincident Mate only makes faces touch; it does not fully define orientation in many assemblies, so parts may still rotate or conflict with other mates.

Quick Fix & Best Practice

• Quick Fix: Edit the mate set in the FeatureManager, suppress conflicting mates, then reapply Mate > Coincident and add a second orientation mate such as Parallel, Perpendicular, or Concentric with Lock rotation if needed.
• Manager’s Verdict: Use Coincident Mate first for most face-joining tasks because it is the fastest standard method in SolidWorks assemblies. Avoid relying on it alone when alignment direction, rotation, or motion control also matters.

FAQ

Is Coincident Mate the same as Merge in SolidWorks?
No, Coincident Mate assembles separate parts; it does not merge bodies.

Can Coincident Mate join non-planar faces?
Yes, in some cases, but the result depends on the face types and assembly intent.

Why do parts still move after a Coincident Mate?
Because the mate removes only certain degrees of freedom and may not fully define the part.

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