Rottler SG7, Operation And Maintenance Manual, Page: 43 / 102

Section 5 Operating Instructions SG7 Manual
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UNIPILOT Centralizing Pilots
Rottler UNIPILOT Solid Carbide Centralizing Pilots are manufactured from fine grain, sintered tungsten
carbide and are ground to a very high degree of accuracy, straightness, and surface finish. They are
designed for a lifetime of precision machining
Pilot Diameter
The straight/parallel part of the pilot that fits in to the valve guide is referred to as the pilot diameter.
Rottler pilots are available in 0.01mm (0.0004”) increments. For best results, the clearance between the
pilot and valve guide should not be more than 0.01mm (0.0004”)
Most new valve guides are manufactured to a nominal size and the valve stem diameters are
manufactured to be smaller than the nominal size to allow clearance for heat expansion of the valve
stem when the engine is operating. For example: a 7mm valve guide has an internal diameter of exactly
7.00mm (.2756”) The valve stem diameter of the intake valve is 6.98mm (.2748”) and the exhaust is
6.96mm (.2740”). In order for the pilot to fit most of the valve guides, the first choice could be UCP0699 to
give .01mm (0.0004”) clearance. If the valve guide is used and has some wear, then the second choice of
pilot could be UCP0700 (0.2756”).
Shank Diameter
The part of the pilot that fits inside the tool holder is referred to as the shank. Rottler offers three different
shank sizes (6.00mm, 9.52mm, and 20.00mm). For longest tool life and best seat cutting results, the
shank needs to go as far as possible inside the tool holder when cutting valve seats or boring out valve
seat housings.
Extended Length (EL) Pilots
Some cylinder heads require extended length pilots because the distance from the top of the valve guide
to the head gasket surface is longer than normal. Normally this distance is about 1.0” - 1.5”, it is when
this distance becomes greater that extended length pilots are needed. The pilots are extended by adding
material below the shank and above the tapered section of the pilot.
If you think you need an extended length pilot, please see the order form in the back of the catalog and
contact Rottler for ordering assistance.
PILOT DIAMETER SHOULD ALWAYS BE GREAT ER THAN VALVE STEM DIAMETER FOR BEST
CONCENTRICITY