Face Grooving & Trepanning Clearance Calculator

CNC Face Grooving & Trepanning Tool Clearance Mechanics

Face grooving (machining an annular circular groove into the end face of a cylinder) requires specialized curved blade holders. Unlike external grooving, the tool blade must curve to follow the circular radius of the workpiece.

1. Curvature Interference (Heel Rubbing)

Because the blade is curved to a specific radius, tool manufacturers designate a strict operating diameter window ((D_{\text{min}}) and (D_{\text{max}})):

• Below (D_{\text{min}}): The inner heel of the curved blade collides with the inner core wall of the groove.
• Above (D_{\text{max}}): The outer back edge of the curved holder rubs against the outer perimeter wall of the groove.

2. The Golden Rule of First Plunge

When cutting a face groove wider than the insert width ((W_{\text{groove}} > W_{\text{insert}})), always take the first plunge at the largest diameter ((D_{\text{out}})) and step inward toward the center. Plunging from the outside in allows chips from subsequent passes to curl freely into the open outer trench, preventing catastrophic chip packing.

3. Chip Evacuation in Deep Face Grooves

Centrifugal force flings chips toward the outer wall of the groove. In grooves deeper than 3 times insert width ((T_{\text{depth}} > 3W)), peck grooving with a micro-retract (0.2 mm) and high-pressure through-spindle coolant (>20 to 70 bar) is essential to fragment chips.