6.5.1 Flashcards
(27 cards)
In thread forms, what are V threads normally used for?
Attaching parts
Aircraft nuts and bolts
In thread forms, what is a buttress thread normally used for?
Takes Axial loads in one direction only
examply Bench vices
What is the purpose of using multiple thread form?
Multiple threads are used to obtain an increase in lead without weakening the screw itself.
(Picture shows after 1 revolution)
Thread pitch is described as being measured between?
The distance from the centre of one crest to the centre of the next crest measured parallel to the main axis.
Pitch is defined as the axial distance between adjacent threads on a helix or screw.
Thread major diameter is described as being measured between?
The largest diameter of the thread measured in a plane normal to the axis.
The lead in a screw thread is described as?
The lead for a screw thread is the axial travel for a single revolution
Example: double thread = 2
2 revolutions will procude 2 pitces
Liner pitch on a screw thread is also called?
Lead
What direction would right hand thread have to be turned to tighten a bolt?
Clockwise
What type of thread has the ISO form?
Metric System
Name the two series of ISO threads in common use?
Coarse Series for general use
Fine series for special applications
What do the parts of the bolt number “1-8 UNC” mean?
1 = 1’’ Diameter Bolt
8 = 8 threads per inch
UNC thread - Unified Coarse
What type of thread system is used on Boeing aircraft?
UNF - Unified Fine
What type of gauges is used to ensure that threads meet the minimum metal limits
specified?
What 2 varieties do they come in?
Not Go Gauges
Come in low addendum or high addendum
What type of gauge is used to ensure that threads meet the maximum metal limits
specified?
Go Gauge
In thread forms, what is ACME threads normally used for?
ACME threads have flat roots and crests and are mostly used for motions of axial drives.
Examply: Trailing edge flap drive
In thread forms, what are Round threads normally used for?
Used for motions of axial drive
especially stressed threads
In thread forms, what are Ball Screw threads normally used for?
Used with re-circulating ball nuts
Aircraft flap drive and stabiliser drive units
Thread minor diameter is described as being measured between?
The smallest diameter of the thread measured in a plane normal to the axis.
Thread crest is described as being?
The crest is the top surface joining the flanks of the thread.
Thread depth is described as being measured between?
The distance between the top of the crest and the bottom of an adjacent root. (both centre)
What direction would left hand thread have to be turned to tighten a bolt?
Anti-clockwise
Why are the roots of external threads always smoothly rounded?
To prevent cracking if the bolt is vibrating and threads are sharp would be hitting off structure.
What are the main types of unified thread used for both ISO metric Threads and Unified inch threads?
UNF = Unified Fine
UNC = Unified Coarse
What happens to threads below 1/4 inch diameter for both UNF and UNC?
Below 1/4 inch diameter the nominaal sizes of both are given as series of numbers from 0 to 12.
