Speeds, Feeds & Machining Parameters Flashcards

What formula is used to calculate spindle RPM when surface footage (SFM) and tool diameter are known?

Answer: RPM = (SFM × 3.82) / Diameter

The standard formula is RPM = (SFM × 3.82) / Diameter, where 3.82 is derived from 12/π.

When machining 6061 aluminum with a 1/2-inch HSS end mill, which SFM range is most appropriate?

Answer: 400–600 SFM

Aluminum is a soft, free-machining material and HSS tools can run 400–600 SFM without excessive heat buildup.

What effect does increasing feed rate have on chip thickness in CNC milling?

Answer: Chip thickness increases

Higher feed rate means the tool advances farther per tooth engagement, producing thicker chips.

The recommended starting chip load for a 1/2-inch carbide end mill in mild steel is closest to:

Answer: 0.004 inch per tooth

A 0.004 inch-per-tooth chip load is a typical starting point for a 1/2-inch carbide end mill in mild steel.

What is the primary reason for reducing spindle speed when drilling deep holes?

Answer: To allow adequate chip evacuation and prevent drill breakage

Deep holes trap chips, and reduced speed combined with peck drilling cycles allows chips to clear before the drill binds or breaks.

Which of the following best describes 'axial depth of cut' (ADOC) in CNC milling?

Answer: The depth the tool engages the workpiece along the spindle axis

Axial depth of cut (ADOC) is the engagement depth measured along the tool's rotational axis (Z direction), controlling how deep each pass cuts.