section 5c Flashcards
how are sheet and flat bar metal measured and box and rod cross sections
l x w x h for sheet
for rods and box sections diameter x length is used
what is the standard measuring system
metric , mm
typical sheet material lengths thickness and widths
thickness starts at 1mm and goes to 6mm
wideh and length go up in 500mm
typical bar metal diameter
3mm to 50 mm for flat bar sections
6mm to well over 100mm for round bar
why is wall thickness for tube and box sections important
too high wall thickness means unnecessary weight and cost
too low wall thickness mean not enough strength
what is gauge measurement and how does it compare to metric
gauge was the measurement of wall thickness as gauge number increase the metric diameter decreases. gauge 10 is about 3mm
measurements needed to select threaded rods
diameter and thread pitch(the distance the nut advances after 1 revolution)
difference between wood screw and machine screws
machine screws have a no point and a finer thread and a parallel shank
what are rivets and two types of rivet
rivets are pieces of metal uses to join other pieces of metal together semi permanently without warping g the metal
pop rivet - a pop rivet gun pushes open the head with the rivet which now domes over the material securing it
cold formed rivet - uses a snap tool to set the rivet in place
types of metal fixing
nuts and bolt : use together with hexagonal profile to apply pressure
machine screw : versatile securer
snap and pop rivet
what is cutting fluid
a lubricant used to cool a drill bit and reduce friction making a smoother cut and stopping overheating and scorching
metal cutting saws
hacksaw and abrafile(coping saw - like)
turning metal
metal is attached onto a chuck which is on a headstock that spins. coolant should be applied and diameter of metal is important for working out the speed of lathe as larger metal should go slower typically
casting
metal is poured into mould to make shapes
the bottom half of mould is called drag, on which green sand Is poured. the top half, the cope, is close and there is holes and ascending points called rise runners and spurs that allow trapped air to leave.
they are sawn off after and recycled
brazing
metalss are joined together using a filler material called spelter, after it is abraded to remove oxide layer. flux is put around the points to stop oxidising again and then spelter flows and cools around the point.
