20XX- Question 7 Flashcards
Identify any two lubricating materials used in engineering machines
PTFE
Oil
Grease
Graphite
Distinguish between the use of a plug gauge and the use of a gap gauge
Plug gauge determines if a hole is within a specific range of limits
Gap Gauge checks if external diameter is within a specific range of limits
State two uses for a chuck guard on the lathe;
Protects user from cutting chips and swarf
Protects user from rotating chuck
Keeps hair and clothing away from the lathe
Has a viewing window which allows you to safely monitor machining
Interlock guards will prevent the machine turning on when not in place
Distinguish between countersink and counterbore holes;
Countersinking is making the hole bigger so countersunk head screws sit flush with the surface of the piece
Counterboring is making the diameter of the hole bigger so a cheese head screw sits flush with the surface of the piece
Name two important properties of cutting tool materials.
Must be harder than the material being machined
Must retain a sharp edge at high temperatures
Must be able to be sharpened or replaced easily
Must be able to withstand shock loads from the machining process
Describe, with the aid of a suitable diagram,
a surface grinding process for a cylinder head.
Surface Grinding
A metal cutting process which produces smooth surfaces
The grinding wheel rotates and cylinder head is fed to and fro consistently
the table is moved across the wheel by a small amount at the end of each stroke
The grinding wheel can be lowered to take a new cut.
Outline two safety hazards associated with using a grinding machine
Tools and metals must be gripped tightly
Loose clothing may get trapped
Needs to be mounted correctly to avoid vibration
Eye protection is needed as small metal pieces are emitted at a high speed
Identify the metal cutting chips shown at A and B and distinguish clearly
between them making reference to material properties. A=continuous chip B=Discontinuous chi[
A – Continuous chip
Soft, ductile material e.g. aluminium
B – Discontinuous chip
More brittle materials e.g. Brass
Analyse the impact on safety and surface finish of the chip formation shown at C. Built up edge
As the built-up edge gets bigger, the cutting edge will not cut well
The surface finish will deteriorate and machining will not be smooth.
The machine will excessively vibrate
Give two advantages and two disadvantages of
CNC machining.
Advantages:
Allows for mass production
Multi tool loading for complex components
Produce parts to maximum accuracy
Disadvantage:
More expensive to purchase and repair.
Higher maintenance than manual machining
Doesn’t eliminate the need for expensive tools
Identify two factors to be taken into account
when selecting CNC machining for the
manufacture of the chess pieces shown opposite.
Choice of material to make the pieces
- Size of the pieces
- Amount of pieces to be made in the set
- Design shape and detail.
