Sandvik Coromant Threading - Manual (Page 41)

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2. Applications – Thread milling
Down milling and up milling
Down milling is when the tool is fed in the direction of tool rotation
and is the preferred method of application - when machine tool,
fi xture and workpiece will allow. Chip thickness decreases from the
start of cut, until reaching zero at the end, which stops the edge
rubbing and burning against the surface before it is engaged into
cut.
In up milling, the feed direction of the cutting tool is opposite to its
rotation.
Entrance into cut – roll in
Make a soft entrance into the cut when circular milling or circular
ramping. This can be done by performing an extra circle, which
results in slow engagement into the material.
For each quarter revolution (90°) during the entrance into cut, the
pitch should be divided by four.
Smooth entrances into the cut are also essential to avoid vibration
and extend tool life.