TM 9-4910-638-14&P
ONE PASS BORING
Many operators prefer to dress a tool in such a way they can produce a desirable finish while taking out .030 to .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 #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
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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