Machining Flashcards
Lathes:
Name 4 materials that can be used
Wood
Metal
Plastic
Ceramics
Lathes:
What is a spindle? What tool is used to operate it?
> Holds the work piece in place
> Chuck tightens it
Lathes:
What is the facing tool?
Squares end of piece my removing material radially
Lathes:
What is the parting off tool?
Cuts off the end by cutting directly into the piece radially somewhere in the middle and allowing the end to fall off
Lathes:
What is the drilling tool?
The work piece rotates whilst the drill bit stays still
Lathes:
What is the boring tool?
Enlarges the internal hole diameter
Lathes:
What is the thread cutting tool?
Moves across the piece at a constant speed to produce a thread
Lathes:
What is the arithmetic mean roughness, its equation, its units and what tool is used and what is the symbol?
> This is a measure of the roughness of a surface
Ra = (1 / n) × SUM[i = 0 ⇒ n] (yi)
- n = number of samples
- yi = radius of sample point from mean surface radius
Units: μm
Tool: Contact profilometer
Symbol: Like a tick but with a line across to form a triangle and the roughness on top of the triangle
Milling:
What is the headstock?
> Where the motor and gearing is held. Also where the tool is held.
It sets the speed of the tool
Milling:
What are the different axes? What moves for each one?
> Table moves for x and y axis
Headstock moves for z axis
A adapter can be used to allow the workpiece to rotate in the b axis
Milling:
What is face milling?
Creates flat surfaces
Milling:
What is end milling?
> Perpendicular to work surface
> Makes trenches
Milling:
What is cutting depth capability?
> The ability of the cutting tool to cut without deflecting
Milling:
What is the slab milling tool?
> This is used to reduce the thickness of a workpiece by removing large amount of material
The putting direction is the opposite of normal milling
What is a work holding device?
Holds parts with awkward geometries
What is a jig?
> Holds work
Positions it on the machining tool
Guides the tool
What is a fixture?
> Holds the work
Positions it on the machining tool
DOES NOT GUIDE THE TOOL
What are the aspects of a fixture?
> Locators
clamps
Setting block (Holds onto work table)
Cutting and chips:
What are the two ways of cutting?
> Orthogonal
> Oblique
Cutting and chips:
What is orthogonal cutting?
> Tool perpendicular to cut direction
Cutting and chips:
What is oblique cutting?
> Tool at an angle to cutting direction
Cutting and chips:
What is are the three types of chips?
> Continuous
Discontinuous
Built up edges
Cutting and chips:
What conditions produce a discontinuous chip?
> Small chip flow angle
Brittle material
Low cut speed
Thick chips
Cutting and chips:
What conditions produce a continuous chip?
> Ductile material
High cutting speed
High chip flow angle
Thin chips
Cutting and chips:
How is a discontinuous chip made?
By the chip facturing
Cutting and chips:
How is a continuous chip made?
By not fracturing
Cutting and chips:
What if discontinuous chips are made with ductile materials?
Then you are using a poor cutting method
Cutting and chips:
What is the benefit of producing continuous chip?
> Good finish
> Long tool life
Cutting and chips:
Describe built up edges
Material builds up on the ‘rake’ of the cutting tool
Coolant:
What is the applications of coolant?
> Reduces friction > Reduces temperature > Stops corrosion > Washes away chips > Reduces built up edges
What are some prerequisites before machining?
> Tool selection > Depth of cut > Cutting speed > Feed > What machine to use
Tools:
What are the 5 types of tools?
> Single point (laithe) > Multi point (mills) > Drills > Reames > Taps
Tools:
What are the main features that are important when selecting a tool type?
> Safety > Time > Quality > Complexity > Price
Tools:
What are some aspects of a workpiece that affect tool selection?
> Hardness of workpiece
Abrasiveness of workpiece
Tensile strength of workpiece
Continuous or discontinuous chips
Tools:
Name 6 important features of a tools material choice?
> Hardness (Harder than work piece) > Operating temp range > Toughness > Abrasion resistance > Pressure resistance > Chemical inertness
Tools:
What are 4 types of materials used for tools?
> Steel alloy
Cast alloy (Lots of carbon)
Cemented carbide
Ceramic tips
Machinability index:
What is it?
The relative difficulty for a material to cut another material when compared with steel
Machinability index:
What is the equation?
MI = ( Cutting speed for tool life of 20 mins / Cutting speed of SAE1112 Steel for 20 mins ) × 100
What is feed rate?
How far the tool moves for one revolution of the part
What happens if there is a high or low speed rate?
High: Affects the finish (makes it worse)
Low: Good for finishing operations (makes it better)
What is affected by cutting speed?
> Tool wear
> Productivity (speed of production)
