It's the Collet, Stupid. Was: It Finally Happened to Me

[Vince Heuring]

Paranoid over my spiral upcut bit climbing out of the collet, see Message ID 230820071732000356% [e-mail] , 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 collet nut.

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 cleaning.

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

[pat]

Excellent points & I would add: The spiral cutter/makers should come clean on their risks and benefits.

(Routers)

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> Here's what I found:

[Swingman]

Absolutely ... thanks for taking the time. Just a reminder to tag on, if you don't mind:

Not a bad idea to do a mental "what if" plan for collet failure/bit creep because it seems that it happens to everyone, to some degree, sooner or later; and _always_ use a push "block" of some type on non-through type cuts rabbets/dadoes/grooves/etc on a router table.