MOST IMPORTANT PART OF THE TOOL
The portion 2 is by far the most important part of the tool and its width and condition will determine
absolutely the quality of cylinder wall finish left by the tool in boring. The following rules apply to
this part of the tool and, if observed, will provide the best results possible.
1- Portion 2 is widened by lapping operation number 2 and narrowed by either 1 or 3 (F or R)
preferably 3, because it is faster.
2- Widening portion 2 improves the finish but at the same time, increases the tendency of the tool
to chatter. The width of portion 2 MUST, THEREFORE, BE WATCHED CAREFULLY.
3- The correct width of portion 2 depends on the diameter of cylinder to be bored. For holes up to
3-1/4", the width on F tool should be about 0.040". For holes larger than 3-1/4" (and longer
than 9") it will be necessary to reduce this width somewhat, the amount depending on the
tendency to chatter at the bottom of the hole. For the largest holes, the width should be about
Careful examination of the tool before lapping will show a gray line along portion 2. This is the wear
that takes place on this keen edge after it has bored a hole. In lapping, you must remove this gray
line in order to restore the KEEN CUTTING EDGE which is of vital importance in getting a good
finish. The keenness of the edge of portion 2 is especially important.
MISCELLANEOUS SUGGESTIONS ON LAPPING
In all lapping operations, lower the jig very carefully to the lapping disc. IF THE TOOL IS
DROPPED ON THE DISC, BOTH TOOL AND DISC ARE SUBJECT TO DAMAGE.
To get the best results in lapping, oscillate the tool with a short, quick movement. Never lap any
more than is necessary. To facilitate lapping operations, keep the steel filed away from the
Tungsten Carbide, similar to a new tool.
The lapping at positions 2 and 3 should be done toward the center of the disc. The lapping at
positions 1 and 4 should be toward the edge.
CARE OF THE DISC:
KEEP THE FELT WICK IN THE LAPPING DISC GUARD SATURATED WITH A GOOD GRADE OF LIGHT
MOTOR OIL (OR SPECIAL LAPPING DISC OIL). IF THE DISC IS USED DRY, THE TUNGSTEN CARBIDE
PULLS THE DIAMOND POWDER OUT OF THE DISC AND WILL SHORTEN ITS LIFE. THE FREE USE OF OIL
ON THE DISC WILL NOT ONLY IMPROVE THE RESULTS, BUT GREATLY PROLONGS DISC LIFE.
OCCASIONALLY THE LAPPING DISC WILL BECOME GUMMED UP AND APPEAR DULL . CLEANING WITH
SOLVENT WILL IMPROVE ITS CUTTING QUALITY. DO NOT PRESS FELT WICK DOWN TIGHT AGAINST THE
LAPPING DISC AS TOO MUCH PRESSURE WILL SERVE AS A BRAKE AND REDUCE THE USABLE POWER
OF THE MOTOR.
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