Mitsubishi 4DQ5 Service Manual download pdf (Page 34)

(c) Grinding the crankshaft

The crankshaft journals and crankpins must

be

refinished

to

a dimension smaller by 0.100 to

0.120 mm (0.00394 to 0.00472 in.) than the

undersize

of

bearings to

be

used.

Example: If

0.50-mm (0.01969-in.) undersize

bearings

are

to be used:

The journals must be refinished to

65

- 0.5 - (0.100 - 0.120)

[2.55905

- 0.01969 -

(0.00394-

0.00472 in.)]

The crankpins must be refinished

to

58 - 0.5 - (0.100 - 0.120)

[2.28346 - 0.01969 -

(0.00394-

0.00472 in.)]

When

grinding the crankpins and journals,

be

sure to produce the same filler radius (shoulder

radiUS)

as

the original one. Too small a radius

of

fillet will result

in

fatigue failure

of

crankshaft

while too large a fillet radius

is

sure to cause the

bearing to ride on the radius and thereby to

result in a bearing failure.

Be

extremely careful

not to grind

off

the radius part beyond the

desired dimension.

An

over-ground radius part

can be corrected only by grinding

off

the

shoulder

face

and this,

if

effected, will present

problems in obtaining a proper end clearance.

Also check the crankpins and journals for

hard-

ness. They should have a hardness

of

620 or

more in terms

of

Vickers Hardness Number.

If

necessary, re-harden the crankpins and journals,

and check them for cracks by conducting a

magnaflux (magnetic particle) test.

Specifications

Unit:

mm

(in.)

Undersize

Journals to

be

refinished to

0.25

!

64

75

-0.015

(25

92 -0.00059)

(0.0098)

. . -0.035 . 4 1-0.00138

0.50

6450-

0

.

015

(2

5393To.00059)

(0.0197)

.

-0.035'

-0.00138

0.75

6425

-0.015

(2 52952

-0.00059

)

(0.0295)

.

-0.035'

-0.00138

-30-

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 119 120

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