diff --git a/web/app/cad/sketch/sketchBoundaries.js b/web/app/cad/sketch/sketchBoundaries.js
index 1454b9cf..9766ce61 100644
--- a/web/app/cad/sketch/sketchBoundaries.js
+++ b/web/app/cad/sketch/sketchBoundaries.js
@@ -1,6 +1,8 @@
-import {circleFromPoints, distanceAB, TOLERANCE} from '../../math/math';
+import {areEqual, circleFromPoints, distanceAB, radiusOfCurvature, TOLERANCE} from '../../math/math';
+import * as vec from '../../math/vec';
 import {iteratePath} from '../cad-utils';
 import NurbsCurve from '../../brep/geom/curves/nurbsCurve';
+import {veqXYZ} from '../../brep/geom/tolerance';
 
 export function getSketchBoundaries(sceneFace) {
   const boundary = {lines: [], arcs: [], circles: [], nurbses: []};
@@ -8,8 +10,41 @@ export function getSketchBoundaries(sceneFace) {
   let _w2sTrArr = null;
   let w2sTrArr = () => _w2sTrArr || (_w2sTrArr = w2sTr.toArray()); 
   for (let he of sceneFace.brepFace.edges) {
-    if (he.edge.curve.impl.constructor.name ===  'NurbsCurve' && he.edge.curve.impl.degree() !== 1) {
-      boundary.nurbses.push(he.edge.curve.impl.transform(w2sTrArr()).serialize())
+    let curve = he.edge.curve.impl;
+    if (curve.constructor.name === 'NurbsCurve' && curve.degree() !== 1) {
+      let curve2d = curve.transform(w2sTrArr());
+      let arcRadius = findArcRadius(curve2d);
+      if (arcRadius !== null){
+        let [from, to] = curve2d.domain();
+        let [A, DA] = curve2d.eval(from, 1);
+        let [B, DB] = curve2d.eval(to, 1);
+
+        let mA = vec.normalize(DA);
+
+        if (veqXYZ(A[0], A[1], 0, B[0], B[1], 0)) {
+          let c = vec.mul(mA, arcRadius);
+          boundary.circles.push({
+            c: {x: c[0], y: c[1]},
+            r: arcRadius
+          });
+          continue;
+        }
+        
+        let centripetalB = vec.normalize(DB);
+        perpXY(centripetalB);
+
+        let proj = vec.dot(mA, vec.sub(A, B));
+        let u = proj / vec.dot(mA, centripetalB);
+
+        let C = vec._add(vec._mul(centripetalB, u), B);
+        boundary.arcs.push({
+          a: {x: A[0], y: A[1]},
+          b: {x: B[0], y: B[1]},
+          c: {x: C[0], y: C[1]}
+        });
+      } else {
+        boundary.nurbses.push(curve.transform(w2sTrArr()).serialize())
+      }
     } else {
       addSegment(w2sTr.apply(he.vertexA.point), w2sTr.apply(he.vertexB.point));
     }
@@ -168,3 +203,27 @@ export function getSketchBoundaries(sceneFace) {
   }
   return boundary;
 }
+
+function findArcRadius(curve) {
+  if (curve.degree() !== 2) {
+    return null;
+  }
+  let knots = curve.knots();
+  let prevRadCur = null;
+  for (let knot of knots) {
+    let [P, D, DD] = curve.eval(knot, 2);
+    let radCur = radiusOfCurvature(D, DD);
+    if (prevRadCur !== null && !areEqual(radCur, prevRadCur, 0.1)) {
+      return null;
+    }
+    prevRadCur = radCur;
+  }
+  return prevRadCur;
+}
+
+function perpXY(v) {
+  let [x, y] = v;
+
+  v[0] = - y;
+  v[1] =   x;
+}
\ No newline at end of file