Section 5 Operating Instructions HP7A Manual
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5-7
Using Diamond Abrasives
General
In the proper application, diamond abrasives are very effective for cylinder honing. The Rottler Precision
Hone Head brings the cost of diamond honing down to a range that is much more affordable. Competitive
hone heads require the purchase of multiple hone heads to cover the same size range as the Precision
Head. The Rottler system is approximately 1/5 the cost.
Because of the long life of diamond abrasives the cost per hole of diamond abrasives is approximately 1/5
of the vitried abrasives.
Diamond abrasives in combination with the Rottler Precision Honing Head make a very rigid honing
head. The system will do an excellent job of truing tapered or out of round holes with little or no operator
attention. An operator can set the roughing and nishing loads and expect the machine to hone the
cylinder to size unattended with little or no attention. It is important to use proper stone pressure when
using diamond abrasives. The roughing motor load setting should be in the 50 - 90% range. The
nishing load should be set in the 20 – 40% area. Generally, the higher the roughing motor load reading
the faster the stock removal. The lower the nishing load is set, the more accurate the bore will be.
The HP7A 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 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 5-10 Ra rougher than after
the break in period. You must hone 2 - 5 blocks before the surface nish stabilizes.
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