96-8000 401
OPTIONS
June 1999
AUTOREVERSING T APPING H EADS
Auto reversing tapping heads eliminate the need for the spindle to reverse at bottom and provide for high
production rates. The reversing function of the tapping head requires an arm to prevent the body from rotating.
This must be considered when changing tools so as not to interfere with operation. The tool block on the VF
Series CNC Mill will accommodate the Tapmatic series of heads. Several sizes are available and should be
chosen dependent on tap size. Choose the head specifically for NC use as they have a 1:1 feed rate. Manual
types have a faster withdraw rate that leads to clatter on the up stroke. A disadvantage to these types of heads
is that when the inevitable crash occurs, you can destroy an expensive device.
Use the G85 or G89 (dwells at bottom) cycle when using a tapping head. Example:
N100 G98 G85 Z-1.0 R0.25 F46.875
THREAD M ILLING
Thread milling uses a cutter formed with the pitch of the thread to mill the thread. The cutters are solid carbide,
fragile and expensive. Some companies sell replaceable insert holders that are more economical. Internal holes
smaller than 3/8 inch may not be possible or practical. It does allow for making thread diameter compensation
and external threads. For large threads, port threads, blind hole threads, thread milling can be the most
economical method.
Thread milling is accomplished with Helical milling. Use a standard G02 or G03 move to create the circular
move in X-Y and then insert a Z move on the same block corresponding to the thread pitch. The feed rate is
selected as in standard milling practice. This will generate one turn of the thread. The multiple teeth of the
cutter will generate the rest. A typical line would be as follows:
N100 G02 I-1.0 Z-.05 F5. (generates a one inch radius for 20 pitch thread)
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