TM 9-4910-579-14&P
CHAMFERING
The knife edge, at the top of the cylinder or sleeve, should be chamfered and this can be accomplished by using the
standard boring tool, but the special 45 degree chamfering tool bit is recommended. No special lapping instructions
will be necessary for the 45 degree chamfering tool and no special jig is required because the tool can be lapped
using the swivel head jig or free hand to maintain the original angle ground on the tool. The chamfering is done by
hand feeding the machine. Care should be taken in setting the tool to be sure the tool is set properly in the boring
head so only the carbide on the tool will touch the knife edge on the cylinder wall.
The tool should be lowered to the top of the cylinder so it is positioned ready to cut and the gear shift lever on the
machine should be set for hand feeding. Turn the handwheel very slowly till the tool starts cutting because jamming
the tool into the top of the cylinder wall will break the tool or produce a rough chamfer.
When ordering the 45 degree chamfering-tool bit specify:
062-1075-02
45 Degree Chamfering Tool
ONE PASS BORING
Many operators prefer to dress a tool in such a way they can produce a desirable finish while taking out 0.030 to
0.040. You will find you can produce a very excellent finish on a cut as heavy as this if the tool is properly dressed
for one-pass boring. The following dressing procedure is recommended.
It is best to start with a roughing tool if you want to lap a one-pass tool because the one-pass tool should have the
#4R position lapped on the front of the tool. The #1 position is lapped as indicated on the swivel head lapping jig,
the #3F position lapped as indicated on the jig and the #2 position lapped as indicated on the jig, but about the
same width as you normally would lap the #2 position on a finishing tool. What you actually have then is a
combination between the roughing tool and the finishing tool. On larger bores or long bores where chatter is a
problem, it is recommended that you lap the #2 position about 1/16 inch toward the #3F mark and #3F position
about 1/16 inch toward the #3R. Lapping the tool in this way will move the #2 and the #3F position back slightly so
the tool will be freer cutting and, therefore, will not have as much tendency to chatter. Lapping the #2 and #3F with
this 1/16 inch relief will enable you to make the #2 considerably wider. See Figure 7, Page - 12 -.
The above lapping procedure, also, is a definite advantage when boring the extremely hard sleeves because the
#3F position will give the cutting edge more support as the tool wears and will cut down on a tendency to lose size
as the tool wears.
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