What is the primary purpose of climb milling, and what surface finish benefits does it provide compared to conventional milling?

The primary purpose of climb milling is to improve surface finish and reduce tool wear by cutting from the thickest part of the chip to the thinnest. In climb milling, the cutting tool's rotation direction is the same as the feed direction, meaning the cutter engages the material with the full chip thickness at the start of the cut. This contrasts with conventional milling, where the cutter engages the material with a gradually increasing chip thickness. Climb milling offers surface finish benefits compared to conventional milling because the cutting force is directed into the workpiece, minimizing vibration and chatter, and resulting in a smoother surface. Because the chip is thickest at the start, it pulls the tool into the material, reducing rubbing and burnishing which can work-harden the surface. It also minimizes the chance of the tool lifting the material ahead of the cut, which can occur in conventional milling and leave behind a rough or uneven surface. The shearing action is cleaner and more efficient, generating less heat and reducing tool wear. However, climb milling requires a machine with minimal backlash, as the cutting forces tend to pull the workpiece into the cutter. Excessive backlash can cause the tool to grab and dig into the material, leading to poor surface finish, tool breakage, or even machine damage. The smoother surface finish in climb milling is desirable in many applications, reducing or eliminating the need for secondary finishing operations.