hunting of tooth-nipping-shot peening-caulking & fullering

2.  HUNTING OF TOOTH GEARS
 SHOT PEENING GEARS & SPRINGS
 NIPPING LAMINATED SPRINGS
CAULKING & FULLERING RIVETS
LIST OF SOME TECHNICAL TERMS :

3.  PURPOSE – is to provide uniform distribution of wear.
 For understanding ,let us consider a pinion has 20 no of teeth and gear 40 no of
teeth,while meshing 2 revolutions required for same pair of teeth to engage.
HUNTING OF TOOTH IN GEARS:
20 TEETH 40 TEETH

4.  Again consider that a pinion has 20 no of teeth and gear has 41 no of
teeth,for same pair has to be engaged ,it requires 41 revolutions.
 That is it takes longer time to meet the same pair which makes the gear
tooth life as high as possible.
 This extra tooth provided to gear is called hunting tooth

5.  FATIGUE- means failure of a material by formation and propogation of crack in
weaker regions( like oil holes,internal crack,keyways ,etc) by tensile stress when
the material is applied to variable loading.
 This fatigue failure occurs at a stress magnitude which is lower than ultimate
tensile strength of material ,sometime the magnitude is lower than the yield
strength
 In other words even ductile material will fail by fatigue in brittle like in nature.
SHOT PEENING:

6.  PURPOSE- to reduce chances of fatigue failure by inducing residual compressive
stress on the material.
 This compressive stress is induced by impinging small steel balls with high
velocity on the surface of the material either by air blast or by centrifugal action.
 shot peening is effective for springs loaded only in one direction.

7. PURPOSE- pre stressing the spring.
 It was found that ,the stresses in extra full length leaves are 50% more than the
stresses in graduated length leaves.
 one of the method to balance this stress is to pre stress the spring by bending
various leaves at different radii before they assembled with the centre clip.
NIPPING:

8. The full length leaf has highest radius of curvature than adjacent leaves.
 this radius of curvature decreases with shorter leaves.
The initial gap between the extra full length leaves and graduated length leaves
before the assembly called nip.
 That is, nipping is the pre stressing the spring by a difference in radii of
curvature.

9. PURPOSE- to obtain leak proof joint(like in boiler,pressure vessel...etc)
 The caulking process is applied to the edges of the lap joint and edges of
strap plate in butt joint.
CAULKING AND FULLERING:

10.  Edges of the pate is approximately beveled 70 to 75 deg.
 the caulking is done by hand hammer or by hydraulic or by pneumatic hammers.
 the blows of the caulking tool causes the contact surface cracks between the two
plates ,between the rivets and the plates resulting in leak proof joint.
 great care must be taken while hammering ,over hammering will injury the
plate,sometimes joint will open instead closing.

11. Caulking must be applied to plates with thickness less than 6mm.
 fullering is similar to caulking ,in this width of the tool is equal to plate thickness
to be hammed.

12. THANK YOU