Surface Finishing & Post-Processing Flashcards

Which type of coolant application method is most effective for achieving the best surface finish in CNC milling?

Answer: Through-spindle high-pressure coolant

Through-spindle high-pressure coolant delivers fluid directly to the cutting edge, flushing chips from the cut and reducing heat at the tool-workpiece interface for better finish.

What surface finish defect is caused by chips being re-cut between the tool and the workpiece?

Answer: Chip scoring or scratching

When chips are not evacuated from the cut zone, they get trapped and dragged across the finished surface, causing scoring or scratch marks.

In CNC turning, which insert nose radius produces the best surface finish at a given feed rate?

Answer: Larger nose radius

A larger nose radius reduces the theoretical peak-to-valley height for a given feed rate, as the wider arc better bridges the feed grooves.

What does an 'Rz' (Rzmax) measurement on a drawing indicate compared to Ra?

Answer: Rz is the average of the five highest peak-to-valley measurements; Ra is the overall arithmetic average

Rz averages the five largest peak-to-valley heights over the evaluation length, making it more sensitive to extreme surface events than Ra.

Which post-processing treatment is most commonly applied to aluminum CNC parts to improve corrosion resistance and surface hardness?

Answer: Type II or Type III hard anodizing

Anodizing converts the aluminum surface into an aluminum oxide layer that is harder and more corrosion-resistant, and is the standard post-process for aluminum parts.

When deburring a part after CNC machining, which edge condition is specified when a drawing notes 'break all sharp edges'?

Answer: A small chamfer or slight radius to remove the burr and prevent injury or stress concentration

'Break all sharp edges' requires a light chamfer or slight radius (typically 0.005–0.015 in) to remove burrs and eliminate stress risers without removing significant material.