CHAPTER 5 - BOLTS, SCREWS AND FASTENERS Flashcards
(27 cards)
FASTENERS
What is the definition of a fastener, bolt or screw?
Fastener: a general term to describe all various types of fastening devices employed in the construction of an aeroplane
Bolt: A threaded fastener with a plain (unthreaded) shank portion
Screw: A fully threaded item regardless of thread size, head style or material
FASTENERS
Apart from their definitions, how else can a bolt or screw by identified?
Any external wrenching is a bolt
Any internally driven item is a screw
FASTENERS
What are the seven common fastener types used?
- Bolts
- Screws
- Nuts
- Wing Nuts
- Studs
- Dowel pins
- Clamps
FASTENERS
How are aircraft hardware identified?
- By its specification number or trade name
FASTENERS
What are the three trade names used to identify threaded fasteners?
AN: Air-Force Navy
NAS; National Aircraft Standard
MS: Military Standard
FASTENERS
Label thesis diagram of bolt types based on their head style:
Match the letter:
Flush head (countersunk bolt/screw)
Internal wrenching bolt
Drilled hex head bolt
Eye bolt
Cleavis bolt
Hex head bolt
EXTRA: AN type
Flush head Screw (Allen type)
EXTRA: MS/NAS type
12 point head bolts
Socket head cap screw
A: Flush head (countersunk bolt/screw)
B: Internal wrenching bolt
C: Drilled hex head bolt
D: Eye bolt
E: Cleavis bolt
F: Hex head bolt
G: EXTRA: AN type
H: Flush head Screw (Allen type)
I: EXTRA: MS/NAS type
J: 12 point head bolts
K: Socket head cap screw
BOLT TYPES
Name the 3 principle parts of a bolt..
1.Head
2.Thread
3. Grip
BOLT TYPES
What are the several parameters in a fasteners specification?
Thread form, shank diameter, head style, grip length, material, surface finish and locking facilities
BOLT TYPES
Match the letter which the correct label:
Headwidth
Grip
Grip
Diameter
Length
Thread
Length
A: Length
B: Head Width
C: Diameter
D: Grip
E: Thread
F: Grip
G: Length
BOLT TYPES
What is the standard angle for a countersunk?
100 degrees
BOLT TYPES
For a countersunk fastener, what are the ‘slot’ forms that could be used?
HINT: 7
- Straight
- Radiuses straight (Hi-Torque)
- Cruciform (cross-shaped)
- Offset Cruciform (Torq-set)
- Offset three-point (Tri-wing)
- Splined (Torx)
- Hexagonal (Allen)
BOLT TYPES
From left to right, label these recess drive slots..
- Straight
- Hi-torque
- Phillips
- Posidrive
- Reed and Prince
- Torque Set
- Tri Wing
- Torx
- Allen
BOLT TYPES
Describe and label views A to G of some common bolt drive types..
View A: Shows an eyebolt, often used in flight control systems
View B: Shows a countersunk-head, close tolerance bolt
View C: Shows an internal wrenching bolt, tightened and loosened using an appropriately sized Allen key
View D: Clevis bolt
View E: torque-set wrenching recess - no taper in the walls of the recess allows for higher torque
View F: external-wrenching head with a washer under the head to provide increased bearing surface
View G: hi-torque style driving slot - Must be installed with a special hi-torque driver adapter and driven with some type of torque-limiting
MARKING OF BOLTS
How are smaller parts of a bolt that can not be marked identified?
From their release documentation or by measurement and careful comparison with the standard table
MARKING OF BOLTS
What do letters A-D stand for with unified thread identification?
A: Unified symbol on head
B: Unified symbol on head
C: Head recess
D: Dog Point
MARKING OF BOLTS
When can alternative parts be substituted?
When indicated in the structural repair manual or under the authority of the Technical Services department
UNIFIED THREAD BOLTS
Describe the code system used for the identification of bolts and screws
Consists of the Standard number followed by the part number of the particular bolt
MARKING OF BOLTS
What should you not do with shear or tension bolts?
Should not replace one with the other
SCREWS
What is the main difference between aircraft bolts and machine screws?
The threads of a machine screw usually runs the length of the shank, whereas bolts usually have an unthread grip length
SCREWS
What are commonly used machine screws? HINT: 5
- Flush-head: used in countersunk holes, available in 82 or 100 degrees of head angle
- Round-head: frequently used in assembling highly stressed aircraft components
- Fillister-head: used as general purpose screws
- Socket-head: designed to be screwed into tapped holes by internal wrenching
- Pan and Truss Head: General purpose screws used where head height is unimportant
SCREWS
What are structural screws used for and how are they constructed?
They are used for assembling structural parts.
They are made of alloy steel and are heat-treated, They have a definitive grip length and the same shear and tensile strengths as the equivalent size bolt
SCREWS
How do Structural Screws differ from structural bolts?
Only by the type of head.
FASTENER LOAD AND TYPES
What are the two loads fasteners are subjected to?
Loads carried along the length of the fastener are TENSION loads
Loads felt across the fastener are SHEAR loads
FASTENER LOAD AND TYPES
What bolt, screw or stud will never fail?
None. No matter how high quality these fasteners are, there is still a risk of failing if installed incorrectly or if misused.
