BY NATE HENDLEY
Multiple factors affect chip breaking, including chip thickness, chip curving, and the material’s properties. But why
is it important to control chip formation and
evacuation? What goes wrong if control is
“If chip breaking is not controlled, it really
slows down the operation because you’ve got
these uncontrolled chips getting caught in
chip conveyors. They also use up much more
volume in the chip bin, so you end up having
to clean out the chip bin much more often.
Long chips also can catch around the tool or
the workpiece, affecting the surface finish,”
explained Kurt Ludeking, product manager
for Walter USA.
If you want to get a handle on chip breaking when turning, observe the colour, size,
and shape of the chips being produced.
“Chip colour and chip size can tell you a
lot about the application. Judging by the
chip colour, you can determine if the heat is
going into the chip or the workpiece,” said
Paul Rice, applications engineer for Kyocera
Precision Tools. “When looking at chip formation, you can determine the proper chipbreaker selection in relation to feed rate,
spindle speed, and depth of cut.”
The shape of the chip also tells you how
well the chipbreaker is working.
As for the specific colours in question, it’s
important to note the difference.
“A dark blue chip could mean that your
surface feet per minute (SFM) speed is too
high, and a silver chip could mean that the
SFM speed is too low,” said Michael Hunter,
business development manager for bore
machining and reaming products at Komet
of America. “For most materials, I try to get a
The same basic rules apply to both turning
and milling applications.
Chip thickness, meanwhile, has a huge
impact on the chip-breaking process.
“[You aim for a] sweet spot. A too-thick chip
gets hard to break because it’s too strong and
you end up getting long, uncontrolled chips.
Conversely, if it’s too thin, the chip is ductile
[the ability of materials to be stretched or
bent without breaking] and you also have
a hard time breaking it. That’s where the
geometry of the insert really comes in to
expand the range of feed rate, depth of cut,
and speed parameters that give you decent
chip breaking,” said Ludeking.
“Chip thickness plays a major role in
chip breaking and shape,” agreed Rice. “If
the chip is too thin, a ribbon effect may
take place, resulting in an uncontrollable
chip that will decrease tool life and create
poor surface finish because the chip will
likely wrap around and/or drag across the
It’s important to match the feed rate to the
Curved or “spiral” chips are created during
and evacuation are
all important to the