Technical data

74
Repair instructions
Crankshaft, renovation
In general, both re-grinding and trueing reduce the
fatigue resistance. So do not re-grind bearing
journals (nitrocarburised in particular) unless there
are strong reasons for doing so. E.g. measurement
faults (wear, ovality, taper) or so serious surface
damage that buffing is not sufficient.
If the crankshaft does not need to be re-aligned
before it is re-ground, it can be ground down to the
second under-dimension before it has to be
nitrocarburised again. If the crankshaft has such
large runout that it has to be re-aligned before
grinding, it should be nitrocarburised again after
grinding.
Work order for renovation
True the crankshaft
NOTE! Only true the crankshaft if it is really
necessary, please refer to “Inspection, crankshaft
and bearings” on page 72.
Do a crack test, please refer to “Crack checking”
on page 73.
Re-grind the crankshaft if necessary, please re-
fer to the next section, and do a new crack test.
Re-do the nitrocarburisation if the crankshaft has
been trued or if it has been ground to the 3rd
underdimension or more. Nitrocarburisation can
be done with gas or salt, the experience and
methods of every heat treatment craftsman are
applicable.
The following two stages are only applicable if the
crankshaft has been nitrocarburised.
Check the runout of the crankshaft again.
Do a new crack test.
Finish off renovation by:
Buffing the crankshaft carefully after any grind-
ing or repeated nitrocarburisation.
Clean the crankshaft carefully from any grinding
residue and other contamination. Rinse and
clean the oil ducts.
Grinding the crankshaft
It is essential for a satisfactory result from grinding,
that the correct method has been used. The following
grinding data are recommended.
Grinding wheel: Naxos 33A60 M6VK or 33A46 M6VK
or Norton 33A60 M5VK or 23A46 M5VK.
Diameter: New disk Ø 36"-42" (914–1067 mm). (The
disk can be used down to Ø 720 mm.)
Peripheral speed:
Grinding wheel .................................. 28–33 m/s
Crankshaft .................................... max. 0.25 m/s
Cooling: 3% oil emulsion (soluble). It is important that
cooling is generous, preferably with oil supply from
both above and below.
The stone should be sharpened with a single stone
diamond.
Peripheral feed rate ...................... 0.1 mm/revolution
Side feed ...................................... 0.2 mm/revolution
Depth of cut ........................................max. 0.03 mm
Crankshaft radii