Shfting Fits And Accesories Flashcards
What are the 5 main types of keys?
Square Pratt/Whitney/boxed/blind Tapered gib key Woodruff Step key
What is the benefit of a spline?
Allows a high torque transfer
What is the rule or thumb for the width of the square key?
1/4 of the diameter of the shaft
Why are woodruff keys used for and what are the numbers on them?
Light applications
The first two digits are width in 32’s and the second two numbers are diameter in in 8’ths
What application are gib head keys used?
What is the typical taper per foot
Used to transmit heavy loads
1/8 in per foot
Or
1in 96
Same thing
Which way do you lock the eccentric lock on a pillow block?
Towards the rotation of the shaft.
When do you use a Quick Detachable (QD) bushing?
Gear reducers, pulleys,
Sprockets
Hubs
Etc
What’s the difference between split taper bushing vs QD bushing?
Split tapers bushings have a split through it and externally and internally keyed
Describe a taper lock bushing?
Usually a series of 3 large set screws. To install bushing and sprocket line up the non threaded holes on the bushing with the threaded holes on the sprocket.
To disassemble move the set screw to the threaded holes on the bushing and tighten
How are tapered sleeve bearing set?
Slide the tapered sleeve on shaft, slide bearing on sleeve, fit lock ring and tighten lock nut.
As you tighten the lock ring it pushes bearing up the sleeve locking it to the shaft and taking up the clearance on the bearing.
What are the different types of locking and positioning devices?
Set screws Tab washers Shear pins Tapered dowel pins Retainer rings Self locking rings Spiral wound rings
What are the two factors that affect shaft selection?
Bending stress
Torsional shear stress
On a 4 inch hollow shaft with a 2” inside bore what is the weight reduction to the Torsional strength reduction?
25percent weight reduction
6.25 percent strength reduction
What is the recommended maximum distance between bearings on a line shaft?
8 ‘
Where is the ideal spot for the bearings on a line shaft?
As close to the gears, pulley’s and sprockets as possible.
What is the purpose of the floating bearings?
To allow for expansion
Where does the fixed bearing go on a line shaft?
As close to the main drive as possible
What bearings are best suited for horizontal line shafts?
Pillow lock
What is added to steel to increase its harden-ability, abrasion resistance, and wear resistance?
Chromium
Describe tolerance?
Tolerance for any dimension is the total variation in size.
Describe fit?
The range of permissible tightness or looseness between mating parts.
What are the three fit types?
Clearance - indicates the shaft is always smaller then the bore
Transition - MMC interference, a minimum bore diameter and maximum shaft diameter.
- LMC clearance fit, maximum bore diameter with minimum shaft diameter
Interference - shaft is always larger than the bore.
What are the 3 main groups for ANSI fits?
Running and sliding fits (RC) Locational fits (LC,LT, and LN) Force fits (FN)
Describe basic size?
The nominal size before tolerances are applied
What is allowance?
The intentional difference between two mating parts at maximum metal condition.
What is Maximum Metal Condition(MMC)?
Largest shaft into smallest hole
What are the three classes of fits?
Class 1 loose fit
Class 2 commercial fit
Class 3 high precision fit
What is the external thread symbol? (Die)
A
What is the internal thread symbol? (Tap)
B
Pitch =?
1
———-
# of threads
What is the symbol for metric threads?
M
How much clearance should be left at the top of the key?
.005”
What is the negative tolerance of cold finished square stock?
.002” to .003”
When are step keys used?
To accommodate a key seat that is wider then the hub
Fixed keys allow the hub to do what?
Move axially
What is used to remove gib headed keys?
Fox wedge
What tools are used to remove keys?
Wedges, slide hammers, key drift
Key ways can be cut with what machines?
Key seat cutter or milling machine
What depth does a broach cut to?
How much depth per tooth?
1/16”
.003”
How many set screws are used to secure hub to shaft and where are they placed?
Usually 2 one placed over the key and the other 90 degrees from the first set screw
What are the two types of shafting?
Hot rolled - needs to be finished
Cold rolled - finished shafting
1018 is?
Low carbon
Low speeds
1045 is?
Medium carbon
High speeds
Shafts are exposed to what stresses?
Bending, shearing and torsional
What can add strength to a shaft where one end is smaller in diameter?
Adding a radius (fillet) at the shoulder area.
What tool can be used to check shaft run out and alignment?
Dial indicator
What is one way a bent shaft can be heated?
Slight heat and peening the bent area
When joint shafts what type of couple is best suited for accurate line up and minor misalignment?
Rigid for accurate alignment
Flexible for misaligned shaft
What is the purpose of a shear pin?
They are meant to shear when somthing jams in the system. This prevents damage to other parts of the system
Tapered dowel pins have what taper per foot?
1/4
On metric fits tolerance what does the upper case letter mean and the lower case?
Upper case is the bore
Lower case is the shaft
Fits can be broken down into?
Running and sliding clearance fits Locational clearance fit Transitional fit Locational interference fit Force fit
What does force fit mean?
Parts are pressed together
What happens for a shrink fit
Hub is heated to expand then when it cools it shrinks to the shaft
Describe expansion fit?
Shaft is cooled to shrink then expands to the hub when it warms back up.
What is the purpose of a shaft?
A mechanical device that transmits motion and power
What is an axle?
A rotating device on which a wheel is mounted
What is a spindle?
A slender pin or rod which turns, or in which something else turns
What is the journal?
Part of the spindle, shaft, or axle that rotates in or on a bearing.
What considerations are taken into account when choosing correct steel for shafting?
Torque Speed Power transmitting and mounting Compression and tensile limits Contraction, bowing, or expansion limits Cost
When would you consider using an alloy shaft?
Where rust and corrosion are great.
What are some of the uses for shafting?
Transfer torque Support pieces of equipment Permit equipment to pivot Extend the length of a drive Change rotary motion to reciprocating
What is the best way to identify shafting?
Proper labeling, proper storage, and good house keeping
What is fatigue?
When the shaft is subject to many cycle of loading.
What is fatigue stress?
The ability of a shaft to resist fatigue
What is radial runout?
Radial runout occurs when the shaft and attatchments are not concentric in their rotation
What is circular run out?
Circular run out occurs because of imperfections
Axial runout?
Axial runout occurs because attatchments do not rotate perpendicularly to the shaft axis
Why are runouts formed?
Bent shaft
Worn bearings
Poor machining
Poor assembly
What is the purpose of a hub?
To enable the component to attach to the shaft
What is the purpose of a coupling?
To connect two shafts together
