Operating Instructions
3-4
HP6A Manual
in that area. For example, if the lights near the bottom of the display move farther to the right than the
rest of the lights, it means the bottom of the bore is a slightly smaller diameter near the bottom. The
same would be true for the top and middle of the bore.
Large Amount of Material Removal:
When you have large amounts of material to remove from a cylinder (.005 and up) the following steps
should be used to maintain size control.
For stock removal of .010 or more it is best to use a two step process. Start with 80 grit stones (.004”
removal per minute) and bring all cylinder to within .005” of the final size. Switch to stones that will leave
you the desired RA value and remove the final amount of material.
When there is less that .010” to remove start with 270 grit stones and bring cylinders to within .002” of
final size. Switch to stones that will leave you the desired RA value and remove the final amount of
material. You can also use the 270 grit stones and bring the cylinder to final size. Then install finishing
stones and use the Plateau Mode of operation to bring the cylinder to your desired RA value.
Common Surface Finishes:
Today’s modern engines are demanding smoother and more precise surface finishes. There are two
commonly used plateau surface finishes in automotive engine cylinder bore finishing today. They are
both described below. The single step, non-plateau finish is no longer recommended for engine cylinder
bores. The processes described below are commonly used in the engine building industry. If the engine
or ring manufacturer recommends a particular finish the engine manufacturers specifications or ring
manufactures recommendation should be followed.
Non-Plateau:
The typical Ra finishes used for a Non-Plateau finish should be in the 16-24 range. A 16-24 Ra finish
leaves adequate peaks to be knocked off during the engine break in period yet is not so rough as to
cause oil burning problems before the cylinder walls have been plateaued by the rings. During initial start
up of the engine the rings will create the plateau by knocking off the peaks of a non-plateau finish. Most
modern ring manufacturers do not recommend using this type of finish.
Plateau
Plateau surface finishes are required to meet the demands of the modern engine designs whether the
engine is a standard automotive engine or a performance engine. There are sophisticated measuring
devices able to measure the details of a plateau finish. Although the cost of these devices have lowered
significantly in the last few years, they are still cost prohibitive to the average shop. Rottler has
established honing procedures, if closely followed, will produce a finish meeting the specifications of the
engine or ring manufacturers.
Below are the current finish recommendations for most automotive engines.
Ra 10 to 20
Rpk 10 to 20
Rvk 30 to 60
Rk 25 to 50
The Plateau finish has become very popular. One of its purposes is to minimize the break-in or ring
seating period. A plateau finish involves the use of a roughing stone followed by a finer grit finishing
stone. When the finishing stone is used, only a few strokes are required to create the plateau. If you
were to continue honing with the finer grit stone you would eventually eliminate the plateau effect and
create a simple non-plateau finish equal in roughness to the finish stone.
Plateau Caution
When using plateau brushes do not exceed 7 strokes. Doing so may cause burnishing of the bore
surface, which lead to improper ring seating and excess oil comsumption.
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