Section 5 Operating Instructions H85A Manual
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5-8
Using CBN Abrasives
Another type of Abrasive is known as CBN or Cubic Boron Nitride. This is a very sharp abrasive unlike
diamond which is relatively dull but very tough abrasive. The CBN abrasive is a very clean cutting
abrasive and doesn’t leave the torn and fragmented metal in cylinder that diamond will leave. CBN is so
sharp that it compares to standard abrasives for cutting action but has the life of diamond abrasive. CBN
won’t last quite as long as diamond or cut as fast so as a rule you would normally use diamond to do
most of the work of stock removal followed by CBN to remove the torn and fragmented metal for a better
surface for ring sealing. If plateau nishes are required we suggest using diamond to hone to size in the
aforementioned grit sizes followed by a CBN abrasive. If you are only doing a one grit nish then we
suggest again honing with diamond to within .0005 to .001 and then following up with a CBN abrasive in
that same grit size. Typically for a nish like this we would recommend a 400 grit CBN abrasive.
The H85A is capable of removing an unlimited amount of material from a cylinder with a high degree of
accuracy. Generally, it is desirable for overall engine block geometry to use a boring machine to bore all
material out except for .003 (.0762mm) of hone stock.
It is important to use Rottler Synthetic Coolant, part number 514-4-71C, when using diamond stones. It
must be mixed with water and maintained properly to give optimum honing results.
Note: When mounting new stones in holders it is recommended that you at stone the back of the stones
to remove any possibility of burrs causing misalignment of stones mounted in holders.
Scratching
Scratching in the cylinder looks as though a single grit of a larger abrasive particle has lodged between
the cylinder wall and the hone head. Often the scratch will be less than one revolution of the hone head
and it will follow the cross hatch angle of the honing machine. Several things can cause this problem.
Improper coolant mix
The ratio of water to synthetic additive to water will change after the initial mix is put in the coolant
tank. A Refractometer can be purchased to accurately check the ratio. When the ratio is measured
as a percentage it should be 5 – 8%. This corresponds to a reading of 3-5 on the Refractometer. It is
important not to confuse the percentage with the true Refractometer reading.
Unacceptable synthetic coolant brand
Lack of abrasive dressing
Dirty Coolant
Breaking In A New Set of Diamond Abrasives
Rottler diamond abrasives are pre-radiused to minimize the breaking in period. When a new set of
diamonds is installed the surface nish obtained on the rst few blocks will be 5-10µin (.13 -.25µm) Ra
rougher than after the break in period. You must hone 2 - 5 blocks before the surface nish stabilizes.
Truing New Diamond Abrasives
On grit sizes 500 and up to 1200 grit we recommend using the lapping compound that came with the
machine to expedite the process.
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