Paranoid over my spiral upcut bit climbing out of the collet, see
Message ID 230820071732000356% firstname.lastname@example.org , I went to
the Borg today and bought a pair of split ring pliers so I could take
my collets apart. BTW, my router was bought four years ago and has seen
only light-moderate use.
See the exploded diagram of a PC collet at
Here's what I found:
Both conical mating surfaces on the outside of the collet were gunked
up, but cleaned up with mineral spirits.
There was a fair bit of fine wood dust in the bottom (top?) of the
Here's what I learned about collets. Of the four slits in the collet,
only one of them goes through to the inner end, the other three are
stopped by stop holes drilled about 1/8" from the end of the collet.
When the collet nut is tightened, it apparently forces both cones of
the collet against the chuck with equal force, provided the collet is
clean and undamaged. On one side of each slit a small lip juts out
into the gap. In one of my gaps the lip was *gone*
and a small sliver
of metal was resting in the gap. The sliver was almost as long as the
collet, as wide as the lip, and measured about .004. Of the four gaps,
three measured .045". The gap that was missing the lip measured .048.
So the lip apparently sheared completely off. The other collet also had
miscellaneous damage to the slits and down around the stop holes.
The point: collets are not immune to damage, especially 1/4" PC ones.
If you're using a bit that has any tendency to pull itself out of the
collet, as the spiral upcut bit does, you would be wise to occasionally
take the collet apart, clean the assembly, and inspect all pieces
thoroughly. At any sign of damage, replace your collets. They're only
$7.11 at Amazon. BTW, the 1/2" collets showed no damage, but did need
PC has some blame here. Nowhere in their instruction manual do they
mention disassembling and inspecting the collets, and most of us would
not think to do so.
Sorry for the long post, but I did want to get to the bottom of this,
and hope you guys will find it useful.
Vince Heuring To email, remove the Vince.