I am having trouble with one particular bit slowly pulling out of the collet
when routing a dado. The bit is a Rockler 5/16" two flute straight (not
spiral) bit with a 1/2" shank and the problem occurs when I have it
installed in my Bosch 1617EVS router in my router table. On three separate
occasions, the dado I was routing was deeper at the finish than at the
start, with the change in depth being gradual. On one occasion the depth
increased about 1/4" over a 10" run. On each occasion the bit was pulling
out of the collet. The first time I assumed I had not tightened the bit
properly, but on succeeding tries I made sure the bit was tight. I have not
had this problem with other bits. Any thoughts on what is happening.
Did you insert the bit all the way into the collet? Try inserting it so that
there is 1/4" in the bottom. If it were all the way, the collet will be pushing
the bit down and unable to tighten all the way. A good method is to put an
o-ring in the base. Home Deport or the like seel them for faucets. OD- 1/2" get
as fat a ring as you can and then place it in the collet and use pencil to
bottom it. Leave it in from thispoint on. When installing bit, press to bottom.
The O-ring will prevent the bit from bottoming out.
if you have a way to measure the shank to thousandths, try that. the
shank may be a tiny bit undersized. if so return the bit.
look for damage to the shank- if there is a burr or something that
would interfere with proper seating. you may be able to correct this,
but if it's a manufacturing defect I'd return it.
clean it carefully with alcohol and a fine brass bristle brush. clean
the collet and the collet seat as well. I have a few brass bore
brushes, meant for cleaning gun barrels. I give the collets and seats
a swipe from time to time.
At the risk of flames, checkIand verify you have your router depth
adjustment locked. Not the router lift, if you have such a setup, the
router depth setting itself. I say this because I have made the same error,
resulting in depth change during routing. Tracked it to a loose locking
lever on the router...it tends to be set and forget when using a lift, but
the lock needs to be set on router itself.
If this doesn't help, then the other replies are more likely your culprit.
I go along with the possible undersize shaft. In my box of bits I had one roman
ogee that did that. My soloution was throw it and get a new one. Anything else
isn't worth the hassatle.
bob making saedust in salem or
I had this happen to me several times when routing dados. I found it to be
what everybody else has said, the shank was a bit undersized. The odd part
is that the last two times it happend it occurred with undersized plywood
bits. Both bits were from the "orange" company that many people seem to be
so fond of. I threw them away and got another brand.......Problem went away.
I use an o-ring to keep the bit off the bottom. I checked the shamk
diameter and found it to be right on. The only thing I could find was
a dark residue in the collet when I cleaned it with laquer thinner. I
did spray some TopCote on the router body a day or so ago. Perhaps I
got some in the collet. Anyway, after a thorough cleaning it worked
This is very interesting - by your description, the bit is falling
upwards into the work (assuming that, like most router tables, yours
has the router mounted upside down).
I tend to agree with the other folk that suggest the bit's shank
is undersize. However, I'd be curious to know what the mechanics
are that are pulling the bit upwards, rather than letting it fall
down with gravity.
If you choose to experiment with the bit, I suspose you could make
a mark on the shank (perhaps with a sharpie pen) at the collet,
and thus verify it is the bit moving out of the collet, and not
On Fri, 23 Jan 2004 20:54:59 +0000 (UTC), John McCoy
if the bit is loose at all in te collet it creeps out of the collet,
irrespective of gravity. I don't have any scientific data about why it
does this, but I suspect that it has to do with the cutting angles
applying pulling force (albeit rotational) outside of the collet.
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