Working Method; Example A - Mira BB-86 Mini Instruction Manual

3 Working method

This picture shows the important working
surfaces. These are the sealing surface of the
block and the sealing and bearing surface of
the sleeve collar.
Rim groove-Ø

3.1 Example A

This example applies to a dismounted engine where the block has been re-surfaced and new sleeves have
been inserted. In this case, the counterbore depth will have been reduced by the re-surfacing of the block,
and needs to be adjusted. Proceed as follows: Clean the sleeves and accurately measure the collar
thickness of each sleeve with the micrometer. Write the measurement onto each sleeve, and number them
in accordance with the cylinder. Subtract the amount of the protrusion specified by the manufacturer from
the collar thickness and write the result onto the surface of the block of each counterbore.
There are 2 different methods for working with the tool:
1. If the same turning tool is frequently used, it is recommended that the vernier be set to 0 (See step
14 on page 25). This can be accomplished after centering of the unit by means of the advancing
mechanism. The required depth can be set and blocked in this position. Now the proper surfacing of
the seat can be started (see „Turning tools and their application" on page 18).
2. If the same turning tool is not used everytime, there is no advantage to be gained by setting the
vernier to 0. In this case proceed as follows: for each counterbore, the existing depth must be
measured and compared with the nominal value and the difference must be written down. After
centering of the unit, the tip of the turning tool must be set above the seat at the precise location
where the measurement was taken. By slightly turning the crank handle and simultaneously
advancing the vertical feed, the turning tool will come in contact with the seat (see steps 11 and 12
on the pages 24 and 25). Thereafter, the turning tool needs to be pushed back into the free area
with the hard metal tip positioned just above of the counterbore seat. Following that, the previously
measured depth difference needs to be set. Finally, the advancing mechanism locking screw must
be blocked and then the seat surfacing can be started.
19 July 2023/v1.7
Depending on the specifications of the engine
manufacturer, the inserted sleeve can be
protruding or recessed.
Engine
block
BB-86 | Serial-No. 865 / 0609 ©
Protrusion
Counterbore-Ø
16
(All rights reserved)
Engine
block