Drilling

Dimensional Accuracy Criteria

These criteria ensure the hole is the correct size and depth.

• Diameter: Must adhere to specified tolerance limits.

• Depth (Blind Holes): Measured from the surface to the full diameter shoulder, not the drill tip point.

• Edge Quality: All holes must be deburred at entrance and exit points to ensure safety and assembly fit.

Geometric Integrity Criteria

These criteria ensure the hole is straight, round, and in the correct location.

• Location/Position: Center axis must be within the defined positional tolerance zone. 

• Roundness (Circularity): Cross-sections must be circular; no ovality or irregularities from vibration. 

• Straightness (Axis Deviation): Axis must not deviate or "drift," particularly in deep-hole applications. 

• Perpendicularity (Squareness): Axis must remain square to the entry surface to ensure uniform clamping 

• Taper: Diameter must remain consistent; no tapering due to tool wear or heat.

Surface and Material Criteria

These criteria relate to the hole's internal condition and the surrounding material.

• Surface Finish: Internal walls must be smooth and free of chatter, swirl marks, or re-cast layers.

• Material Soundness: No evidence of micro-cracks, tears, or work-hardening (discoloration) from improper feeds/speeds.

• Cleanliness: Holes must be delivered free of chips, swarf, and residual cutting fluids.