Design Atlas
한국어
⚙ Product & industrial design

Fillet vs. chamfer

필렛 vs 챔퍼

Two ways to soften a sharp edge — a fillet rounds it with a curve, a chamfer slices it flat at an angle.

Also known as: 모따기Round vs. bevel edge
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html
<div class="fc-wrap">
  <div class="fc-panel">
    <svg viewBox="0 0 100 100" class="fc-svg">
      <path class="fc-shape" d="M20,80 L20,20 L80,20 L80,80 Z"/>
      <path class="fc-edge" d="M20,20 L80,20"/>
    </svg>
    <span class="fc-cap">sharp — 90°</span>
  </div>
  <div class="fc-panel">
    <svg viewBox="0 0 100 100" class="fc-svg">
      <path class="fc-shape" d="M20,80 L20,36 A16,16 0 0 1 36,20 L80,20 L80,80 Z"/>
      <path class="fc-edge" d="M20,36 A16,16 0 0 1 36,20"/>
      <line class="fc-dim" x1="36" y1="20" x2="36" y2="36"/>
      <text class="fc-r" x="40" y="30">R</text>
    </svg>
    <span class="fc-cap">fillet — round</span>
  </div>
  <div class="fc-panel">
    <svg viewBox="0 0 100 100" class="fc-svg">
      <path class="fc-shape" d="M20,80 L20,36 L36,20 L80,20 L80,80 Z"/>
      <path class="fc-edge" d="M20,36 L36,20"/>
      <text class="fc-r" x="20" y="30">C</text>
    </svg>
    <span class="fc-cap">chamfer — flat</span>
  </div>
</div>
css
.fc-wrap{display:flex;gap:clamp(6px,3vmin,20px);align-items:center;justify-content:center;width:100%;height:100%;padding:clamp(8px,3vmin,16px)}
.fc-panel{flex:1;max-width:200px;text-align:center}
.fc-svg{width:100%;height:auto;display:block}
.fc-shape{fill:var(--accent-3);fill-opacity:.16;stroke:var(--fg);stroke-width:1.4;stroke-linejoin:round}
.fc-edge{fill:none;stroke:var(--accent-2);stroke-width:2.6;stroke-linecap:round;animation:fc-pulse 1.8s ease-in-out infinite}
.fc-dim{stroke:var(--muted);stroke-width:.7;stroke-dasharray:2 2}
.fc-r{font-size:9px;fill:var(--muted)}
.fc-cap{display:block;margin-top:.6em;font-size:clamp(9px,2.5vmin,13px);color:var(--muted);letter-spacing:.02em}
@keyframes fc-pulse{0%,100%{opacity:.55}50%{opacity:1}}

A fillet rounds an edge with a radius (R); a chamfer slices it flat at an angle, usually 45°. Both look like they're doing the same job — softening something sharp — but the reasons and manufacturing paths differ.

A fillet is comfortable to hold, keeps paint or coating from peeling at the edge (a sharp edge gets a thin, fragile coat that chips first), and in injection molding reduces stress concentration so the part doesn't crack right there — which is why almost every inside corner of a plastic part is filleted. A chamfer, by contrast, self-aligns a part into a hole during assembly, is often cheaper to machine (a simpler tool path than a fillet on a mill), and reads visually as "precision-machined" on metal parts.

In CAD, switching between a fillet and a chamfer command on the same selected edge is a routine move, and changing the value — radius, or chamfer distance and angle — parametrically updates the whole model.

When to use

Fillet edges that hands or fingers touch; chamfer edges that need to self-guide assembly or where machining cost matters.