What does( 3/4''-10 unc -2a x 1 1/2'' )stand for? - Answers 3/4''= Nominal diameter
10 = Threads per inch
UNC = thread style (Unified national Course)
2= Class of fit
A= External thread (b= internal thread)
1 1/2''= length (depth of full threads in hole)
class of fit 1,2,3,4,5&6 - Answers class 1 fit= maximum looseness in mating threads
class 2 fit= average fit little play in mating threads
class 3 fit= no looseness in mating threads.
class 4 fit= precision threads, usually cut and ground
class 5 and 6 fit= embellishments of class 4, but the most precise and accurate threads.
what does M8x1.25x50mm stand for? - Answers M= Metric
8= nominal diameter in mm
1.25= the pitch
50mm= length of fastener
machine screws - Answers special group of screws 3/8'' or less in diameter
to find the diameter of a machine screw - Answers multiply the screw number by 0.013
add 0.060
Ex:
#6 machine screw
6 x 0.013 = 0.078
0.078 + 0.060 = 0.138''
self tapping machine screw - Answers is installed into a drilled hole slightly smaller than the major
diameter of the screw
find the tap needed for a drill - Answers TDS= Nominal dia - pitch
, lubrication does what? - Answers reduces friction and increases life by reducing wear
sliding friction - Answers contact spread over a large surface, pressure per sq in usually light
rolling friction - Answers rolls over a surface, area of contact is quite small pressure load is high
fluid friction - Answers two surfaces in contact, a film of oil is formed ,filling up the depressions and
covering the projections on both surfaces.
adheasion - Answers forces cause unlike material to stick together
cohesion - Answers cause molecules of like material to stick together
viscosity - Answers the resistance to flow
choosing viscosity - Answers depends on speed, load, temp, pressure, and environment
how is viscosity measured? - Answers dynamic and kinematic
kinematic viscosity - Answers affected by the density of the oil measured in centistokes
calcium soap grease - Answers requires a small amount of water to stabilize. recommended for damp
conditions with low heat
sodium soap grease - Answers soluble in water but has high temperature range. only used in dry and
high temp conditions
aluminum soap grease - Answers gives stringiness and is used where adhesiveness is important. water
resistant not recommend for high temps.
lithium and barium soap grease - Answers water resistant and high temperatures the most commonly
used soap grease.
dropping point - Answers the temperature that a grease will become fluid enough to drip.
what is the most commonly used lifting rope? and why - Answers the wire rope
it is stronger than natural and synthetic ropes and gives good warning of failure when defective.
construction of wire rope - Answers small diameter wires wound around a small core to create a strand,
strands wound around a steel or fiber core.
wire ropes with steel core are - Answers crush resistant
abrasion resistant
flexibility
strength