Ferrous & Non-Ferrous Material Properties Flashcards

Which non-ferrous alloy is commonly used for bearings in CNC machine spindles due to its low friction coefficient and good embeddability?

Answer: Babbitt metal (tin-lead alloy)

Babbitt metal is a soft tin- or lead-based alloy used in plain bearings because it conforms to the shaft and embeds contaminants rather than abrading the journal.

What does the term 'temper' refer to when applied to aluminum alloy designations (e.g., 6061-T6)?

Answer: The heat treatment and mechanical working condition of the alloy

The temper designation (T1–T10) describes the sequence of heat treatment and/or cold working applied to achieve specific mechanical properties.

A part made from AISI 4340 steel has been hardened and tempered. Which property has been primarily optimized?

Answer: High strength combined with toughness

4340 is a nickel-chromium-molybdenum alloy steel that after hardening and tempering delivers exceptional strength-to-toughness ratio, used in gears and shafts.

Which ferrous material class is used for cutting tool inserts in CNC machining due to its extreme hardness and wear resistance?

Answer: Cemented carbide (WC-Co)

Cemented carbide inserts (tungsten carbide in a cobalt matrix) offer hardness near 90 HRA and maintain cutting ability at high temperatures.

Brass (copper-zinc alloy) is preferred over bronze for many plumbing fittings CNC-machined at high volumes because it:

Answer: Machines more freely and is less expensive

Brass, especially free-cutting brass (C36000), has excellent machinability ratings near 100% and is cost-effective for high-volume CNC turning of plumbing parts.

Which property of a material is described as its ability to resist deformation under a sustained load over time at elevated temperature?

Answer: Creep resistance

Creep is the slow, time-dependent plastic deformation of a material under constant stress, especially significant at elevated temperatures.

When a CNC machinist notices that a drilled hole in a stainless steel part has a work-hardened skin from a previous operation, the best approach for reaming is to:

Answer: Use a larger ream allowance and ensure constant chip engagement to avoid rubbing

Using sufficient stock for the reamer and maintaining constant feed prevents the tool from rubbing on the work-hardened surface, which would worsen the condition.