CNC Ferrous & Non-Ferrous Material Properties 5

Question 1

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

Accepted Answer

Babbitt metal (tin-lead alloy)

Answer

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.

Question 2

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

Accepted Answer

The heat treatment and mechanical working condition of the alloy

Answer

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

Question 3

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

Accepted Answer

High strength combined with toughness

Answer

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

Question 4

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

Accepted Answer

Cemented carbide (WC-Co)

Answer

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

Question 5

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

Accepted Answer

Machines more freely and is less expensive

Answer

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

(CNC) Computer Numerical Control Machinist Technical Practice Test

(CNC) Computer Numerical Control Machinist Technical Practice Test

CNC Ferrous & Non-Ferrous Material Properties 5