How do I create a fillet between two lines in XyzPilot?

Use Arc/Fillet,L,L with the two line references and the required radius. XyzPilot computes the fillet arc analytically — no selector needed for perpendicular lines.

How do I create rounded corners in a CNC profile?

Use Arc/Fillet,L,L to create a fillet arc at each corner, then use Trim operators to remove the corner material. This creates a clean closed profile with rounded corners ready for CAM toolpath generation.

Arc/Fillet,L,L

Fillet Arc Between Two Lines

Creates a fillet arc of specified radius between two intersecting lines. The arc is tangent to both lines at its start and end points. Used for rounded corners in CNC profiles.

What It Does

The Arc/Fillet,L,L operator creates a circular arc that is tangent to two intersecting lines simultaneously. The arc radius is specified by the operator. The arc centre is computed analytically — it lies at distance R from both lines.

The fillet arc is a product-tier entity — it is persistent and tracked by the dependency system. After creating the fillet, use Trim operators to remove the corner material from the original lines.

No selector needed for perpendicular lines — the fillet position is uniquely determined by the two lines and the radius. For non-perpendicular lines, a Flip selector may be available to toggle between corner solutions.

Syntax

Arc/Fillet, L1, L2, R

Parameter	Description	Required
`L1`	First line reference (e.g. L0, L1…)	✓ Yes
`L2`	Second line reference (e.g. L1, L2…)	✓ Yes
`R`	Fillet radius in millimetres	✓ Yes
`Flip`	Toggles to the opposite corner solution (angled lines only)	Optional

Quick Input Panel

L:   [first line reference]
L2:  [second line reference]
R:   [radius value]

Worked Examples

Example 1 — Right-Angle Corner (Most Common)

Setup:
  L0 = Horizontal line at Y=0
  L1 = Vertical line at X=100
  Intersection at (100, 0)

Arc/Fillet, L0, L1, R=10
→ A0: Centre=(90, 10), Radius=10
       Start point: (90, 0)   ← tangent to L0
       End point:   (100, 10) ← tangent to L1
       Sweep: 90° CCW

Example 2 — Large Radius Fillet

Setup:
  L0 = Horizontal line at Y=0
  L1 = Vertical line at X=80

Arc/Fillet, L0, L1, R=25
→ A0: Centre=(55, 25), Radius=25
       Start point: (55, 0)
       End point:   (80, 25)
       Sweep: 90° CCW

Example 3 — Angled Lines

Setup:
  L0 = Horizontal line at Y=0
  L1 = Line at 45° through (50, 0)

Arc/Fillet, L0, L1, R=15
→ A0: Arc tangent to both lines, R=15
       Centre computed analytically
       Sweep determined by line angle

Full Corner Workflow — Rounded Rectangle

The typical workflow for creating a rounded corner in a CNC profile:

Step 1 — Create the rectangle
Rectangle/P_TL=(0,60), P_BR=(100,0)
→ L0 (bottom Y=0), L1 (right X=100)
   L2 (top Y=60),  L3 (left X=0)

Step 2 — Create fillet arcs at all four corners
Arc/Fillet, L3, L0, R=10  → A0 (bottom-left)
Arc/Fillet, L0, L1, R=10  → A1 (bottom-right)
Arc/Fillet, L1, L2, R=10  → A2 (top-right)
Arc/Fillet, L2, L3, R=10  → A3 (top-left)

Step 3 — Trim the corners
Trim/L0, to, A0, End       → removes bottom-left corner
Trim/L0, to, A1, Start     → removes bottom-right corner
Trim/L1, to, A1, End       → removes bottom-right corner
Trim/L1, to, A2, Start     → removes top-right corner
[repeat for all corners]

Result: Closed profile with four 10mm radius corners.
        Ready for CAM toolpath generation.

Always create all fillet arcs before trimming. Trimming changes the line endpoints, which may affect subsequent fillet calculations.

Analytic Rule

For two intersecting lines L1 and L2 with fillet radius R:

1. Compute offset lines parallel to L1 and L2
   at distance R (on the interior side of the corner)

2. The intersection of the two offset lines
   gives the fillet arc centre C

3. The tangent points are the perpendicular
   projections of C onto L1 and L2

4. The arc sweeps from the L1 tangent point
   to the L2 tangent point

Result: Arc centre, start point, end point, and
        sweep angle are all exact analytic values.

FAQ

How do I create a fillet between a line and a circle?

Use Arc/Tanto,L,C,R — the arc tangent to a line and circle operator.

How do I create a fillet between two circles?

Use Arc/Tanto,C,C,R — the arc tangent to two circles operator.

What if the radius is too large for the corner?

If the fillet radius is larger than the available space (the offset lines do not intersect within the geometry), XyzPilot returns an error. Reduce the radius.

Do I need to trim after creating the fillet?

Yes. The fillet arc is created as a separate entity. The original lines still extend to their original intersection point. Use Trim operators to remove the corner material and create a clean closed profile.

What is the difference between a fillet and a chamfer?

A fillet is a rounded arc. A chamfer is a straight angled cut. Use Arc/Fillet,L,L for rounded corners and Chamfer/Between,L,L for angled corners.