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Tutorial Intermediate ⏱ 15 minutes

Pocket Machining Geometry

Create a rectangular pocket profile with island — the complete geometry needed for pocket roughing and finishing toolpaths in CNC milling.

What You Will Build

A 80×60mm rectangular pocket with a 20mm radius circular island at the centre. Complete geometry for pocket roughing and finishing CAM toolpaths.

Operators Used

Rectangle/TL,BR Circle/Centre,R Arc/Fillet,L,L Trim/L,to,A
01

Create the Pocket Boundary

Create the outer boundary of the pocket — the wall that defines the pocket extents.

Point/0, 0, 0 → P0 Point/80, 60, 0 → P1 Rectangle/P0, P1 Quick Input: P: 0 P2: 1 → L0: bottom (0,0)→(80,0) → L1: right (80,0)→(80,60) → L2: top (80,60)→(0,60) → L3: left (0,60)→(0,0) Pocket boundary: 80×60mm
02

Add Corner Fillets to the Pocket Boundary

Add 8mm radius fillets to the pocket corners. The fillet radius should be slightly larger than the cutter radius to ensure the cutter can reach the corners.

Arc/Fillet, L3, L0, R=8 → A0 [bottom-left] Arc/Fillet, L0, L1, R=8 → A1 [bottom-right] Arc/Fillet, L1, L2, R=8 → A2 [top-right] Arc/Fillet, L2, L3, R=8 → A3 [top-left] Trim all corners (8 trim operations as in Tutorial 1)
Pocket corner radius must be ≥ cutter radius. Use R=8mm for a 16mm diameter end mill.
03

Create the Central Island

Create the circular island at the centre of the pocket. The island is a boss that the cutter must machine around.

P_centre = (40, 30) [pocket centre] Circle/Centre, P_centre, R=20, 0 → C0: circular island, centre=(40,30), radius=20mm Clearance from island to pocket wall: Horizontal: 40 - 20 = 20mm (left and right) Vertical: 30 - 20 = 10mm (bottom), 60-30-20 = 10mm (top)
04

Verify Clearances

Check that there is sufficient clearance between the island and the pocket walls for the cutter to pass.

Minimum clearance = 10mm (top and bottom) Cutter diameter = 16mm → cutter radius = 8mm Clearance check: 10mm clearance > 8mm cutter radius ✓ Cutter can pass between island and pocket wall Measure → Distance Click C0 (island), Click L0 (bottom wall) → Distance from island edge to wall: 10mm ✓
05

Create the Toolpath Boundary

The CAM toolpath for pocket machining requires two closed profiles: the outer boundary and the island. Both are now defined.

Outer boundary (pocket wall): L0-A1-L1-A2-L2-A3-L3-A0 [closed profile with fillets] Inner boundary (island): C0 [closed circle] CAM setup: Pocket operation: outer boundary inward Island avoidance: C0 outward Depth: as specified in CAM setup Cutter: 16mm end mill, R=8mm
06

Add a Keyway to the Island

Optionally add a keyway slot to the circular island for a shaft key.

Keyway dimensions: 6mm wide, 3mm deep Line/Parlel, XAxis, D=33 → L4: top of keyway at Y=33 Line/Parlel, XAxis, D=27 → L5: bottom of keyway at Y=27 Line/Parlel, YAxis, D=46 → L6: end of keyway at X=46 Trim/L4, to, C0, End, XLarge → L4 trimmed to circle Trim/L5, to, C0, End, XLarge → L5 trimmed to circle Trim/L6, to, L4, End → L6 trimmed to top Trim/L6, to, L5, Start → L6 trimmed to bottom Keyway profile complete.
The keyway is cut into the island. The CAM toolpath must machine the keyway as a separate operation.

Tips & Best Practices

  • Pocket corner radius must be ≥ cutter radius — the cutter cannot reach tighter corners.
  • Island clearance must be > cutter radius on all sides for the cutter to pass.
  • Create the outer boundary and island as separate closed profiles for CAM.
  • Verify all clearances with Measure → Distance before generating toolpaths.
  • Use the Toolpath Simulator to verify the pocket toolpath before machining.

Operators Used in This Tutorial

Rectangle/TL,BR

Rectangle

Creates the pocket boundary.
Circle/Centre,R

Circle by Centre and Radius

Creates the circular island.
Arc/Fillet,L,L

Fillet Arc

Creates pocket corner fillets.
Trim/L,to,A

Trim Line to Arc

Trims lines to arc boundaries.

Related Tutorials

Tutorial

Rectangle with Filleted Corners

Create the base rectangular profile.
Tutorial

Parallel Offset Profile

Create offset profiles for wall thickness.
Tutorial

Bearing Pocket

Create a circular pocket with a keyway.

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