6.5.2 Bolts, Studs and Screws Flashcards
What is meant by the grip length of a bolt and what is it measured in under the imperial system?
The grip length is the unthreaded portion of the bolt.
Measured in 1/16 ‘’ BAC
or 1/8 ‘’ AN
What is meant by the diameter of a bolt and what is it measured in under the imperial system?
The Diameter is the largest distance of the unthreaded/threaded portion of the bolt.
Measured in 1/8 ‘’ for both BAC and AN
Name two types of anticorrosion treatment used in the manufacture of bolts?
Cadmium Plating
Chrome Plating
Anodising
Nitrating
Is a slotted engine nut approved for airframe use?
A slotted engine nut is designed for aircraft engine applications and is not approved for airframe use.
What do the following abbreviations represent?
NAS
MS
ASTM
SAE
AN
AS
BAC
NAS = National Aerospace Standard
MS = Military Standard
ASTM = American Society for Testing and Materials
SAE = Society of Automotive Engineers
AN = Air force Navy
AS = Aeronautical Standard
BAC = Boeing Aircraft Corporation
Identify the following bolts?
- Raised circle on its head:
- Double dash on its head:
- Single raised dash on its head:
- Triangle with an x in the centre:
- Drilled Hex Head Bolt
- Aluminium Alloy (2024 bolt)
- AN Standard steel bolt (Corrosion Resistant)
- NAS close tolerance bolt
What type of nut would you use to lock a plain nut with?
Aircraft check nut ( pal nut / jam nut)
Used to jam against a plain nut to lock it to a bolt so that it will not move.
What class of fit are aircraft screws?
Aircraft screws are manufactured with a class 2 (free fit) thread fit for ease of assembly.
What class of fit are aircraft bolts?
Aircraft bolts are manufactured in the class 3, medium fit.
What is the main difference between a machine screw and a structural screw?
Are Structural screws threaded their whole length?
Structural screws are manufactured from higher strength metals and are used in shear loading only.
Also, structural screws are not threaded their whole length
In fastening devices what are studs?
Studs are headless bolts that are threaded for their entire length or at both ends.
What is the name given to the threaded area of a stud installed in the component?
Answer unsure.
How long will high temperature self-locking nuts remain serviceable?
Once they are not damaged, not melted and retain their locking properties.
They are serviceable.
Self locking nuts remain serviceable as long as it is not possible to turn the nut onto the bolt fully without the use of a spanner.
Above what temperature are low temperature self-locking nuts “fiber type” subject to deterioration.
120^C
The plastic inserts may melt above this temp.
Do the threads on a bolt cut or impress themselves against the “fiber type” insert in a locknut?
The threads on a bolt impress themselves on a ‘‘fiber type’’ / plastic insert.
12 point head bolts are used normally in what areas of the aircraft?
Engines
Clevis bolts are used under what type of loads?
Used only in shear application
SHould be in same direction as gravity.
What does the bolt number represent:
AN4-7A
AN - Airforce Navy specifications
4 - diameter in 1/16 ‘’
7 - Shank in 1/8 ‘’
A - Means the shank of the bolt is undrilled
(no letter would mean it is a drilled shank for split pin or locking wire)
What is meant by the Recess of a bolt?
The Recess is the indentation in the head, used in the identification or to drive the bolt.
Identify the following bolt:
AN Standard Steel Bolt (Corrosion Resistant)
Identify the following bolts:
Left to right:
AN Standard Steel Bolt
AN Standard Steel Bolt
Special bolt
Identify the following bolts:
Ledt to rigth
NAS close tolerance bolt
Aluminium Alloy (2024) bolt
Identify the following bolt:
Magnetically inspected
Identify the following bolt:
Reworked Bolt
What does an aircraft plain nut do?
Has no means of positively locking it to the bolt so it must be used with either a lock nut or a check nut.
What are the different classes of fit?
Class 1 = Loose fit
Class 2 = Free fit ( Aircraft screws)
Class 3 = Medium fit ( Aircraft bolts)
Class 4 = close fit
What are the uses of Machine Screws?
Machine Screws are generally used in non-structural applications and are threaded for their full length.
Class 2 fit.
In fastening devices what are studs?
Studs are headless bolts that are threaded for their entire length or at both ends.
What is the general guide in terms of nuts and how far onto bolts they should go?
As a general guide, 2.5 threads should be shown after the nut has been tightened onto a bolt.
(Always refer to the applicable and current aircraft manual for official guidelines)
When is a wing nut used?
A wing nut is used on a component that is removed frequently.
What are the 3 basic types of screws used in aviation?
Machine Screw
Structural Screw
Self-tapping screw
What are the two basic types of self tapping screws?
Type of fit?
- Type ‘A’ has a sharp point or gimlet and course threads
- Type ‘B’ has a blunt point and a finer thread than the type ‘A’
Self tapping screws are a class 2 fit?
What angle are all countersunk holes at in aviation?
100 degrees
What is a caution with self tapping screws?
What is a hexagon Head bolt?
A hexagon head bolt is an all-purpose structural bolt used in general application involving tensile and shear loads.
When is a countersunk Head bolt used?
Used in a bolted joint that is subjected to severe loads reversals and vibrations.
What are the following indications on bolt heads (Recess)?
Cross or Asterik
Single dash
Two dashes
A triangle surrounding the cross or asterik
No marking on the bolt head
Nickel Steel
Corrosion resistant steel bolt
Aluminium Alloy
A close tolerance bolt
Low strength bolt (not approved for aircraft use)
