Which practice is considered safe for a milling cutter or face mill when approaching a workpiece?

The reasoning for considering a face mill taking a cut of at least 1/2 to 2/3 of the diameter as a safe practice relates to the tool's effectiveness and the resultant stability during machining. When a face mill engages the workpiece with a cut of more than half of its diameter, this maximizes the contact area and provides better support for the tool.

This practice helps in uniform chip removal, reduces vibrations, and allows for a smoother operation, all of which contribute to improved tool life and surface finish. Additionally, it ensures that the cutting forces are distributed more evenly, minimizing the risk of tool breakage or workpiece damage.

In contrast, entering the workpiece at a high rate of speed can lead to excessive wear on the tool and the potential for dangerous situations if the tool grabs or jerks. Climb milling on machines without backlash control can lead to inaccuracies or even damage due to unexpected tool movement. Plunge cutting with a four-fluted gashed end mill may not be the safest method, as it can lead to tool stresses that are difficult to manage, especially if the design and material being cut are not conducive to this style of cutting.