Hello friend's 

 Let's discus about locking device 
for to add 2 Part can be use locking device 
(his says screwed or threaded)
Locking device have two types 
as (1) For forever add 
and (2)temporarly add
for Forever joint can be use as welding 
and For temporarly  joint 
the temporarly joint as Whenever you can do two part  Apart  
the automobile  Can use his colled (locking device)
 From Which bangles his colled nt 
Whoes outer side Is Bangles his colled bolt 
Exaple 
crest     55   Pitch    flank  
                                    depth
                  rool                     
fig 9,1-v. Thread              
1 (B.S.W.)- His angLes 55stays 
His Numbar of threads (T.P.l.) Remains short 
such nt can be use for jJeneral work