Flash Cards from 1994 prep course
where would a bottoming tap be used?
When you have a blind hole. tap can’t go all the way through
Tap drill size for 3/8-16 UNC thread?
3/8 - 1/16
= 0.375 - 0.0625
=.3125
= 5/16
What speed do you run a 1/2” bit drill when drilling low carbon steel?
R.P.M = (4 x Material cutting speed) / (DIA. of Drill bit)
=(4 x 100)/0.5
= 800RPM
MAT’L cutting speed
low carbon = 100sfpm. cast iron = 80sfpm. aluminum = 200 sfpm. Stainless = 55 sfpm
What are the fire extinguisher letters and symbol meanings?
A - Green Triangle - natural product - wood, cardboard
B - Red Square - Combustible - gas, paint, cleaning products
C- Blue Circle - Electrical - wire short, t.v.
D- Yellow Star - Combustible metals - magnesium, aluminum
Whatb speed do you run a 1/2” machine reemer compared to a regular drill?
1/2 to 2/3 the speed
What is the typical included angle of a drill for general purpose drilling?
118deg
what is the speed of a 5/16” drill in low carbon steel
R.P.M = (4 x Material cutting speed) / (DIA. of Drill bit)
=(4 x 100)/0.3125
= 1280RPM
Tap drill for a M12 x 1.75 thread
O.D - Pitch
12-1.75
=10.25mm
How far above the roof/platform should a ladder extend?
3 feet/ladder rungs
Where should a D-ring for a safety harness go
Center of back
How far from the wall should a ladder be if it extends up 24 feet?
4:1 ratio
=24/4
=6 feet
What standard do safety glasses comply to?
C.S.A
Canadian standards association
What instrument would you use to measure the shoulder of stepped hole to withing 0.001”?
Depth micrometer
What wrench would you use to ensure even uniform tension is applied to all bolts
Torque wrench
What type of bolt would you use to fasten a steel plate to wood? wood to a steel plate?
1.Lag Bolt
2. Carriage bolt
What pitch of hacksaw blade would be used to cut pipe?
32 pitch(32 teeth per inch)
fine pitch
precision tooth form
which way do you cut with a hacksaw
forward
what is the first tap you use when threading a hole
taper tap
how are numbers on a depth micrometer displayed differently than a standard micrometer?
the lines and read in reverse. numbers are covered up.
When measuring a bore diameter what instrument would you use?
inside micrometer
the distance between two thread peaks is called?
the pitch
What would you use to measure clearance between parts?
feeler gauges
what is the included angle of a UNF thread
60deg
what type of thread is used for the lead screw on a lathe? and what is the included angle?
ACME thread
29deg
What are grinding wheels made from for cutting steel? soft metals and sharpening carbide tools?
1.aluminum oxide
2. silicone carbide
ratio of a dividing head used on a milling machine?
40:1
Why and holes reemed?
For precision holes
drill a hole 1/64th undersized and then reem to prevent cracks and to improve stress relief
Weight of one cubic foot of steel
490 lbs/cu. ft
What does I.W.R.C mean in wire ropes
Independent Wire Rope Core
what does 6 x 19 mean with wire rope?
6 - strands
19 - wires per strand
how is rope measured?
across it’s greatest diameter
how much Crosby clips reduce the strength of a wire rope?
20%
What is the S.W.L of a 1/2” wire rope?
S.W.L = safe working load=breaking strength
Formula = S.W.L = d^2 x 8
=0.5 x 0.5 x 8 = 2 tons
What is a snatch block used for?
NOT used for lifting.
It is used to change the direction of pull on a load line and to gain mechanical advantage.
when dealing with wire rope.
1.What is left/right lay?
2. what is regular/lang lay?
Left lay or right lay refers to the direction of the strands.
In a regular lay rope, the wires in the strands are laid in the opposite direction as the strands in the rope.
In a lang lay rope, the wires in the strands are laid in the same direction as the strands in the rope.
Examples of fiber rope, Natural vs synthetic?
Natural - Manila, hemp, cotton
Synthetic - polyproline nylon
S.W.L of 1” wire rope with an eye made with crosby clips
S.W.L = safe working load=breaking strength
Formula = S.W.L = d^2 x 8
=1.0 x 1.0 x 8 = 8 tons
8 tons x 20% deficiency
8.0 x 0.80 = 6.4 tons
safety factor when lifting people
10:1 ratio
S.W.L of 1/2” rope when lifting personnel?
S.W.L = safe working load=breaking strength
Formula = S.W.L = d^2 x 8
=0.5 x 0.5 x 8 = 2 tons
safety factor when lifting people 10:1
=2 ton / 10 = 0.2 tons = 400lbs
What knot to use when joining two ropes of the same diameter
reef knot.
When lifting a load what happens to the the stress on a sling as you decrease its angle from vertical?
As the angle gets less the stress in each leg will increase.
As you go from vertical to more horizontal the stress on the strap increases and as a result the lifting potential of the strap decreases.
What type of knot provides a non slip loop what is used for hoisting
bowline knot
What is a sheet bend used for?
Joining 2 ropes of different diameter
what is a spreader bar used for
used to suppport/lift long loads. keeps the lift horizontal
by how much % does a choker hitch reduce the lifting capacity
30%
Name the3 most common sling configuration
single vertical hitch
Choker hitch
Basket hitch
What is the recommended sling angle? what is the critical angle?
Recc- 45%
Critical - 30%
what is the minimum thickness of a scaffold plank and what is the most common wood used?
2”x10” is minimum
Fir wood is first choice
What is the safety factor for a sling
5:1
How many Crosby clips are used on a 3/4” wire rope
4 clips
1/8-7/16 =2
1/2-5/8 = 3
3/4-1 =4
how far apart should crosby clips be spaced?
6 x dia of rope
in hoisting and rigging what are thimbles used for?
protects the eye of a sling from abrasion and rubbing
hand signal for stop
arms crossing and moving out horizontally
hand signal for travel
move arms in circular motion around each other in front of body
hand signal for raise load
one hand, index finger pointing up, move in circular motion
using a block and tackle that has a mechanical advantage of 10, to lift 5 tons. what is the pull on the lead line?
5 ton = 10000 lbs
10000/10(M.A)
=1000lbs a.k.a 1/2 tons
what is the purpose of a tagline
control/guide the load from a safe distance. keep the load straight or turn it.
6 foot prybar had a 2” long toe. what is the weight of load you can lift if you exert 150 lbs on the end of the prybar?
6 foot = 72”
72” x 150 lbs = 2” x load weight
load weight = (72x150)/2
load weight = 5400lbs
what are the two major stresses a shaft is subjected to
twisting - the shafts resistance to turning
bending - caused by the weight of the shaft to sag between bearing support OR a sidways pull on a shaft
Why do pump/drive shafts often have a center drill hole on the end of the shaft?
for mounting on a lathe to check for shaft deformation
how much will a 10 foot shaft expand when there is a temp rise of 50deg. the material has a coefficient of expansion of 0.000006.
C.O.E x length x deltaT
0.000006 x 120” x 50deg
=0.036”
what are keys used for on a shaft
provide positive drive with no slippage
2 basic style of keys
rectangle and woodruff
what is a parallel key?
a square key - all sides are even
what is a pratt and whitney key
a boxed/square key that has both ends rounded
what is a taper key
bottom and sides are square, top edge is tapered so it wedges in and is self holding
what is a gib key
like a rectangular key but one end has a raised square of material for easy for removal
what si the taper of a taper key
1/8” per 12”
1:96
what is a feather key?
key with counter bored holes drilled in to screw/mount the key to the shaft
what is a saddle key
the key rides on top of the shaft, bottom of the key is ground concave so it sit in position
when would you use a step key
when the hub and the shaft are differently sized
how many set screws and at what position should they be placed on a shaft
2 set screws 90deg apart
What does a key number 608 designate
6 - width of key in 32nd - 6/32 = 3/16th
08 - length of key in 8ths - 8/8 = 1inch
so woodruff is 3/16th wide and 1 inch long
What does a key number 1212 designate
12 - width of key in 32nd - 12/32 = 3/8th
12 - length of key in 8ths - 12/8 = 1 1/2inch
so woodruff is 3/8th wide and 1.5 inch long
clearance fit vs interference fit
clearance - When the dia. of the hub is larger than the shaft. no force is required to put parts together
interference - when the hub is the same size or smaller than the shaft to external force is required to put parts together
what are 4 methods for shrink fitting. to install a interference fit assembly
Oven, induction heater, oil bath, oxyacetylene dry ice, freezer, CO2, liquid nitrogen
what is ambient temperature
the surrounding air temperature
room has ambient temp of 70 deg. how much will a steel shaft with a 3” bore expand when heated to 480 deg.
C.O.E of steel = 0.00000633
c.o.e x length x deltaT
0.00000633 x 3” x (480-70)
=0.0073”
why do induced draft fans require much more maintenance than other fans?
the fan is subject to more exhaust gas/material/dust moving across/over the fan. as these contaminants build up they lead to imbalance and damage.
