Threaded Fasteners

Question 1

what type of clearance is required for unthreaded fastener holes? (holes for bolts)

Answer 1

‘generous’ clearance

Question 2

can threaded fasteners be used to locate parts? why or why not?

Answer 2

they require clearance on at least one of the parts

Question 3

practical design considerations of threaded fasteners

Answer 3

need to access the head of the nut/bolt
tightening tool head is often larger than nut/bolt head
tool must be able to turn at least 30 degrees

Question 4

what would an ‘m’ on a bolt head represent?

Answer 4

mild steel
not very strong
Sp < 300 MPa

Question 5

how would you find the proof strength from the Gr P.Q

Answer 5

proof strength = PxQx10 MPa

Question 6

the proof strength is slightly _____ than the yield strength

Answer 6

less

Question 7

Px100 gives you what?
(in reference to the grade stamp on a bolt)

Answer 7

ultimate tensile strength

Question 8

advantage of a nylock nut

Answer 8

nylon collar creates friction with the teeth of the bolt which prevents loosening

Question 9

limiting factor of nylock nut

Answer 9

limits tension due to friction

Question 10

what is considered failure for pressurised and non-pressurised joints?

Answer 10

pressurised: failure by loss of clamp force
non-pressurised: failure concerning yielding of bolt in tension

Question 11

why is large joint stiffness ratio undesirable?

Answer 11

they result in a small increase in the external forces creating large increases and fluctuation in the bolt force

Question 12

how can you achieve a small joint stiffness ratio?

Answer 12

ensure that clamped members are much stiffer than the bolt